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TEACHERS' GEOGRAPHY 



MAN AND CLIMATE 

WITH PRACTICAL EXERCISES 



THIRD EDITION 



MARK JEFFERSON 

w 
Michigan State Normal College 



Published by the Author at 

YPSILANTI, - MICHIGAN 

1911 



<A<1^ 



Copyriglit, 1911 by Mark Jefferson 



C)CI.A2785{U 



PURPOSE 

These notes are planned to facilitate the work of the Teachers' course for the student 
by putting in his hand a statement of principles that will be amplified and illustrated in the 
class room, and formulating the illustrative exercises he is to perform. 

The work is a Teachers' Course in the State Normal College. That means that it is 
12 weeks of work thought essential to the professional preparation of the teacher who can 
give but one term to this department. The time period is not deliberate choice, but 
traditional. The 12 weeks' course is our unit. Given that unit it has seemed most 
prudent to subdivide the professional work into: 1 The Teachers' Course, and. 2 General 
Geography. We wish our students to have a somewhat modern point of view in geography. 
We have therefore to treat of the principles involved in modern doctrine on the subject. 
The time limitation narrows this course to a portion of the subject matter; the distribution 
of Man, and Climate, the first controlling condition of that distribution. 

Other portions of the subject will be treated in General Geography, three courses 
of 12 weeks available for students who can give more than one course to the work. 



1. If Geography is concerned with the earth and man, as soon as we have some idea 
of the distribution of land and water on our globe, it becomes of interest to know where 
this man is. A glance at the map on page 10 (Figs. 3 and 4) is necessary at this point. 
The depth of sh?des on it corresponds to the density of the population of the various 
regions, close and crowded where the map is black, many men living in little space, and 
grading through lighter shades to blank areas which are practically uninhabited, though 
crossed from time to time by the solitary hunter or prospector or wandering bands of nomads. 
A very hasty glance at this map shows the great unevenness of our occupation of the earth. 
If man is gregarious he has at the same time a tendency to fall into groups that are 
singularly isolated. We were aware that more than half of mankind lives in Asia but we 
may not have realized how persistently Asiatic men crowd into the southeastern corner of 
their continent, leaving a good half of its surface uninhabited. Again we knew that the 
Australians do not rival the Chinese in numbers but we had no idea that all the men of 
that part of the world lived close to the southern and eastern coasts of their Island -con- 
tinent and on the neighboring islands. We knew of Europe as the home of many, many 
nations, and nations that have figured much in history, literature, art and science, but was 
it clear to our minds how completely man and his works have occupied that continent and 
that continent alone? Europe is the only continent with almost no desert spaces. Ninety 
percent of the surface of the continent is settled. The rugged, rocky uplands of Scandinavia 
and the frozen Arctic plain of northern Russia are the only bits of Europe to deny abiding 
places to Europe's peoples. This is the more noticeable in the light of the wide blank spaces 
on the map of each of the other continents, ranging from two and a half millions of square 
miles in Australia to nearly eight millions in Asia, space enough for the whole continent of 
North America. There are not people enough in the whole world to settle Asia as closely 
as Europe is settled. 

2. In the New World lands, in which I include South Africa and Australia with the 
Americas, another glance at the map shows but thin settling, so different from Eurasian 
grades that one cannot help thinking of the newness as a possible explanation of their scanty 
peopling. In that case there are to be vast enlargements in the total of humanity in these 
new fields. But we should not form hasty conclusions as to the effect of time. The facrts 
of Asia and Europe are opposed to such a view. Contrasts of density there are by no means 
to be explained in terms of time elapsed. Mesopotamia and most of North Africa have had 
time and history enough. Yet how thinly are they peopled to-day! In general it is the 
lands about the Baltic and the North Sea, new lands all in European history, that far excel 
in density the historic shores of the Mediterranean. Italy is only an apparent exception to 
this statement. It is true that .she is only surpassed on the North Sea by Britain, Holland 
and Belgium in regard to density of population, but it is to geographic conditions and not 
length of time that she owes this ; geographic conditions that she alone of Mediterranean 
countries shares with central and northern Europe and that must have contributed no little 
to her ancient dominance. In Asia, too, the central deserts have historic remains of high 
antiquity, though the populous lands of to-day are also old. 

3. The effects of natural laws are as complex as their causes. Time has great changes 
in store for the peopling of the newer lands. There will be great growth in numbers, great 
adjustment to environment, which will set in operation in the New World those processes 
long at work in the Old. These processes, this adjustment to environment, all this is 
geography, a science whose problems are admirably set before us by the seeming lawlessness 



of man's distribution on the earth. We need not hesitate to read in the thorough peopling 
of Europe alone among the continents the unconscious verdict of millions of vigor- 
ous, restless homeseeking men that they have found in Europe man's fittest environ- 
ment, a verdict justified by the careful investigations of modern scholars. So in Asia the 
southern and southeastern border has greatest geographic fitness. These considerations 
form a logical introduction to the facts of geography; a criterion for the importance and 
rank in the science of those facts is given at once in their ability to answer the question 
that here arises: wherein consists the fitness of this region for man? Before attempting to 
answer this question let us point out that the brevity of new world history has not hin- 
dered geographic agencies from guiding the spread of culture here. The guidance has 
not always been so effective, has not taken a form so final, but the problems here are 
identical. The examination of new world landscapes, the investigation of new world 
resources have been barely begun. Man is rich in all these lands, which include Aus- 
tralia and South Africa as was said above. He does not yet feel the stimulus of need. It 
is therefore a more superficial and temporary aspect of his environment to which he reacts, 
but the reaction is no less certain. 

4. For North America it needs but a glance at the rainfall map at page 12 to perceive 
the great similarity between it and the population map. Rains have a very final word in 
assigning Man permanent abodes in his gropings about the Earth. The 100th meridian 
(Fig. l) sharply separates rainy lands from arid in all of the continent north of the thirtieth 
parallel, and inexorably bounds even thin populations on the west, as the homeseekers who 
ventured into western Kansas in 1890 found to their cost. But while man has not closely 
occupied parts of the continent that have less than 20 inches of rain neither is his further 
grouping porportioned to the grades of rainfall above 20 inches. Empty places occur in 
nearly all latitudes. The small ones in Florida and Central America are not due to defect 
of rain. The very dense areas are not found occurring with very heavy rainfall. It is 
wholly doubtful if man's prosperity is favored at all by more than 40 or 50 inches of rain. 
For the rest, the conditions of the two areas of very dense population are pretty strongly 
contrasted. In Porto Rico, man lives easily amid the exuberance of the tropics, in a fruitful 
land with a climate that imposes on man little need of shelter and clothing. The much 
larger area toward New England on the other hand is in that belt of energetic American 
life between Baltimore and Boston in which resides so much of American culture, thrift 
and business; where are so many large cities, so many great universities, so many associ- 
ations with great men and great deeds in the history of the United States. South of the 
thirtieth parallel the rain falls from the Atlantic to the Pacific and men have no such east 
and west division as in Canada and the United States. The islands of rainfall that accom- 
pany the chief mountain ranges of the western plateaus are matched by islands of thin 
population which streams even beyond the rainbelts along the river valleys that lead flood 
waters out into arid country and make agriculture possible with irrigation. Canada is 
seen to be largely rainless and empty. 

5. Labrador is apparently well watered enough for occupation but suffers the dis- 
advantage of a thin soil coating a wilderness of rocks, like most of the country north of the 
St. Lawrence and the line of Great Lakes between Lake Ontario and the mouth of the 
Mackenzie river. So along the Pacific coast of Canada and Alaska there is rain enough. 
Overmuch mountain and bare rock may have deterred man from settlement. Norway, 
which has a similar position in Europe, has 96 percent of her surface uninhabitable moun- 
tains. So with abundant rains, she has but 18 people to the square mile in a continent 



where the average is a hundred. Yet even so moderate a peopling as Norway's — it would 
correspond to the dots of our diagram — has been the result of a thousand years of 
national life. And that thousand years has been of much significance. All America 
is so new to civilized man that no energetic effort has yet been made with us to occupy 
any but the best lands. It is for this reason, in part, that the population is still denser 
toward the New England region, the points of early settlement and near approach to the 
mother country. 

It is by no means clear that this is always to be so. A glance at the world map does 
indeed show that none of the world's very dense populations is wholly without contact with 
the sea, yet they do extend inland in Southern Germany, India and China eight hundred to 
a thousand miles, and one sees no reason why the Atlantic density of population may not 
some day extend along the Mohawk valley and the shores of the lower lakes. The moun- 
tains of Alaska may not always deter men, but today their influence is strong. 

Thus mountains are seen to blow hot and cold, draw men and repel them. In the 
arid lands of the western United States the cooling lift they give the winds brings very 
welcome rain. There every mountain is a green place, wooded and grassed, an island in 
the desert expanse. Men live there of necessity, not on the mountains, that men rarely 
do, but in the valleys between, and therefore always in limited numbers. The Rocky 
Mountain valleys support the people of the western States, but their population will never 
be dense. Further east where the lowland rains are sufficient, one may see on the large 
diagram how the population thins at the Ozarks, the mountains of Virginia, West Virginia, 
in the Catskills and Adirondacks of New York, and in the mountains of northern New 
England. 

6. Other areas of thinner population in the Eastern United States occur in the 
swamps along the Mississippi in Arkansas and Louisiana. Here is too much water rather 
than too little, as in the Everglades at the tip of Florida, almost without people for lack of 
drainage. 

Turning our glance westward from Florida toward the Pacific we find Lower Califor- 
nia without water or people, but in Central America again an unpeopled strip across Yuca- 
tan coincides with a strip of exceptionally heavy rainfall. The rain belt does not, however, 
continue along the Honduran and Nicaraguan coasts which are equally without popula- 
tion. The diflBculty here is probably the great heat, more intense on the Caribbean than 
on the Pacific coast. The name Mosquito coast, applied to the Nicaraguan strip, has its 
own implications. Here plants may thrive better than men as on the plains of the 
Amazon. 

The dense population about the city of Mexico occupies a basin of rather less than 
twenty inches of rain, but is easily watered from the surrounding heights. 

7. Men seek the heights in the tropic regions not directly because of the heat below, 
but rather because of the overwhelming luxuriance of the vegetation and the prevalence of 
human ailments in the combination of heat and reeking dampness on the lowlands. To 
clear away the forest is a heavy undertaking even in our northern open woods. The 
opening up of Michigan was not to be compared for rapidity with that of the prairie states 
where the land was ready for the plow when the owner came to it. In the wet regions of 
the tropics the forests are inconceivably dense. To leave the trail is not merely difficult, 
it is a sheer impossibility. Plants grow not merely on the ground but on each other until 
the whole space between the tree top and the ground is filled with a mat of interlacing 
growths. To make a clearing in such a tangle is a huge labor, to maintain it an endless 



one. Kipling's " Letting in the Jungle " well conveys the idea of vegetation fairly oblit- 
erating a village. Perhaps the day will come when these forests must be tamed, but in 
America four centuries of Latin dominion has made no impression on them. Dominica 
in the West Indies is as impassable off the narrow road as when Columbus gave it a name. 

8. It cannot be accident that the peopling of Australia, South Africa, and Madagas- 
car is all to the east. Let us see therefore what peculiarity each of these has in its eastern 
parts. Each has abundant rain on the east and steadily diminishing rain to the westward. 
A glance at some political map of South Africa is instructive. On the west, reaching from 
the Atlantic more than half way across the continent, are the great deserts of German 
Southwest Africa and Bechuanaland, then succeed for another considerable distance the 
semi -arid uplands of the Boer country further east, now Orange river and Transvaal col- 
onies, and then, under the rugged slopes of the Drakensberg, by which the plateau breaks 
down on the east, the well watered gardens of Natal. This thrice repeated topographic, 
climatic, and distributive group of features is a proper characteristic of an eastward rota- 
ting earth. Were the motion reversed the three populous regions would be blighted with 
ensuing drought. It is not by chance that our people thin out so suddenly at the hun- 
dredth meridian, that the Pacific coasts of America are populated for thirty degrees on each 
side of the equator, then desert for the next ten degrees toward the poles in each hem- 
isphere, thence peopled again beyond the forties. Surely the great things in geography 
are the agencies that have governed such a distribution of mankind. 

9. Upon careful examination of data that are now fairly obtainable for the whole 
world, at least as far as broader features go, it appears that the first requisite for a great 
population group is broad soil -covered plains for their home; the second, sufiicient rain- 
fall on these plains; the third, a temperature neither too low for plants nor so high as to 
provoke vegetation to become man's oppressor rather than his servant. History reveals 
man in the old world settling down more and more firmly and growing more and more 
prosperous under these conditions. The new world has many a hint of similar tendencies. 

Next to broad plains for the development of such populations as are characteristic in 
Europe comes the need of suflBcient rain. In this Europe is singularly happy. She suf- 
fers less from drought than any other continent. Only the Spanish interior and southeast, 
and the steppes of east Russia are limited in population from this cause. Thus it happens 
that Russia's population leans so decidedly westward as the map shows and that of the 
Iberian peninsula is so close a reflection of its rainfall and therefore marginal. So much 
of Australia is arid that only her eastern border can ever become populous, despite her 
newness. 

10. The distribution of people in South America is somewhat peculiar. The densest 
population is rather over twenty-six to a square mile, that is, a little more than the aver- 
age density of the United States. The patches of dense population are seen at once to lie 
always within 400 miles of the sea. A northeast southwest line through the center of the 
continent would have a region to the southeast with almost all its dense patches on the 
coast; another to the northwest with none at the coast, but all near it. What determines 
this arrangement? The mountains of the continent: for South America though endowed 
with two of the greatest river systems of the world, leaves the greatest of these solitary 
and deserted and finds its mountains all -determining for the homes of its nations. 
A glance at any map showing relief reveals the fact that the populations of the northwest 
lie along the high valleys of the Andes, and that the thin peopling, indicated by the 
dots, observes a similar behavior down to the tropic of Capricorn. In Peru and Ecuador 



the moderate population reaches the coast, while in Columbia and Venezuela the transition 
is from moderate along the central Andean chains to thin at the coast and on the plains of 
the Amazon. 

The vast basin of the Amazon is seen to be all but deserted. Brazil has its people 
gathered along its eastern border, where it, too, is high, but the people have not drawn 
away from the coast as on the Pacific. Tropical South America has its people in the five 
mountain republics of the northwest — Venezuela, Columbia, Ecuador, Peru and Bolivia, 
and on the elevated eastern sea border in Brazil. The Amazon basis is a great hinterland 
on which all have claims, for the most part ill defined or in dispute, but in which none 
have any significant number of citizens. It is in complete possession of aboriginal sav- 
ages, apart from isolated trading posts along the waters. The equatorial position, of 
course, is the cause. The dominant races seek the mountains to escape from the heat and 
moisture of the lowlands. The tropical Andes are the great rain producers of their conti- 
nent in the cooling lift they give to the trade winds that blow from the Atlantic against 
their eastern slope, but their upper valleys are drier and are the truly temperate regions of 
the world. North of the twentieth parallel South America hardly knows greater differ- 
ences between summer and winter temperatures than five or ten degrees. A lowland heat 
of 75 to 85 degrees proves very favorable to rubber, sugar cane, coffee and cacao, but man 
ever since Inca days has preferred the drier, cooler mountains, always with the same nar- 
row range. In the Andean republics the denser populations live where the thermometer 
ranges mostly between 50 and 60 degrees or 55 and 65 degrees. 

11. South of the tropic the Andes serve to part men as well as the waters. The high 
valleys there are too bleak for permanent homes. There the Andes are a wall, a boundary. 
They are not essentially in Chile and the Argentine, but east of Chile and west of the Ar- 
gentine Republic, a relation entirely different from that which prevails further north. The 
lowlands in the south have distinct summers and winters, hot and cool respectively. 
They are somewhat short of moisture, notably in the western Argentine plains, under 
the wind shadow of the Andes, for in this region of westerly winds the rains come from 
the Pacific or from disturbances that sweep eastward across the continent. The plains here, 
narrow in Chile, broad in the Argentine, are the home of prospering, thriving men, of 
communities that are taking part in modern life, with schools, railroads and active com- 
merce, that puts them in contact with the other active peoples of the earth. 

12. There are not very many people in the world in comparison with its area. 
Texas would hold them all and give each man, woman and child a square seventy feet on 
each edge. They could stand much closer than that. Two thousand people can stand in 
a mile-long line very easily. They will have two and two thirds feet between the centers 
of their bodies. A square mile so covered would have four millions on it, and the whole 
sixteen hundred millions of the world's people could stand in the little state of Rhode Isl- 
and, and have abundant room to spare. 

13. But standing room is a very different thing from living room or "Sustenance 
Space ", the area from which a man can draw his food and clothing. This varies greatly 
with the man's occupation, being very large for hunters and fishers, smaller for grazing 
nomads and lumbermen; smaller still for agriculturists. Thus it happens that there is a 
close relation between density of population and the occupations widely prevalent through 
a region. Generally these relations hold all over the world. Thus hunting and fishing 
may support from two to eight people per square mile and they must of course be savages 
or barbarians, lacking as they do agriculture and the manufacturing arts. Grazing and 
lumbering may prevail with densities of 8 to 26 people. So all four of these occupations 



are likely to occur in one part or another of the dotted areas of the map (p 10, see numbers 
on the Legend.) The student should check this up somewhat for himself by examining 
regions where he knows that lumbering, for instance, is general to see what the map indi- 
cation is there. 

14. For agriculture, predominant where the population densities are from 26 to 250, 
we distinguish two types. These might be called large farm and small farm agriculture, 
but better names are extensive and intensive agriculture, putting the emphasis on the de- 
gree of thoroughness with which the ground is worked. The extensive or large farm agri- 
culture characterizes regions where the density of population is from 26 to 125 persons to 
the square mile. This is typical of southern Michigan. Here the farm house is apt to 
have four indwellers, and the numbers allow from 6 to 31 such farms in a square mile. 
Each farm must run therefore from 106 to 20 acres in size, as a matter of fact we 
know they are mostly of forty, rarelj^ of eighty acres. In the same way we may estimate 
that the intensive farming prevalent with population densities of 126 to 250 people to the 
square mile implies farms of ten or twenty acres. But the}' will be more thoroughly tilled 
and will yield much larger crops for the same area. Note the following figures from the 
1909 Year Book of the U. S. Department of Agriculture. They are averages for the 
twenty years 1889 — 1908 of the yields of five important crops in bushels per acre for 
United States (extensive), and Germany and United Kingdom (intensive) : 





U. S. 


Germany 


U. 


Kingdom 


Potatoes 


90 


197 




186 


Wheat 


14 


29 




33 


Oats 


29 . 


50 




45 


Barley 


26 


34 




35 


Rye 


16 


25 




27 (Ireland) 



Two thirds of our farms are of more than 50 acres each; more than two thirds of 
British farms are of less than 50 acres and of Germany's four fifths are of less than twenty- 
five acres. 

15. For densities of population above 250 per square mile the predominant pursuits 
are the manufacturing industries except in eastern Asia, where an agriculture so intense 
prevails that there is nothing like it elsewhere, with the population running to 300 and 400 
to the mile. 

If we add to these grades of density cities, with over ten thousand to the mile, but too 
small of area to be perceptible on a map so small as these, we have in the population map 
a rough means of judging what men do as well as where they live. 

16. NORTH AMERICA 

DENSITY OF POPULATION. (Fig. 1) 

1. What one word best describes the density of population of North America north 
of the 50th parallel? 2. In what states does a very dense population occur? 3. 
Name all regions of dense population. 4. About what proportion of the United States 
is moderately peopled? Where? 5. What grade of population is most widespread west 
of the 100th meridian? 6. Explain (5) by Rainfall map. 7. Compare the density 

of population in the United States east and west of the 100th meridian. 8. Explain (7) 
by Rainfall map. 9. State and explain the density of population of Florida. 10. 

What is the principal grade of population south of the 30th parallel? 11. Why is there 
not the same difference at the 100th meridian as in the United States? (See Rain map.) 
12. State the east and west arrangement of grades of density of population in Central 
America and explain it. 13. What style of agriculture appears to be most prevalent in 

North America? 14. State the density of population along the Pacific coast from 
Vancouver Island to Lower California. 15. Explain it. 16. In general how well 

are the West Indies settled? 17. Why is northern Mexico so thinly peopled? 18. 
Where do the people of Canada mostly live? Why? 19. What are the main agricul- 
tural regions of the United States? 20. What appear to be the occupations of northern 
and southern Michigan? 




160 170 160 IBO MO 130 120 IIP 100 90 ao 70 60 50 40 30 



Fig. 1 



aO 10 IP 20 30 4-0 .50 6£ 




Fig. 2 



17. DISTRIBUTION OF POPULATION IN EUROPE- (Fig. 2) 

1. Name countries with regions of very dense population. 2. Name countries 

where scanty population occurs. 3. What countries ha\'e regions of thin population? 

4. Describe the largest area of very dense population in Europe. 5. What grade of 
population is most widespread about the shores of the Baltic Sea? 6. Locate the three 
population -regions of the Baltic. 7. Describe the density of population about the 
North Sea. 8. Describe the distribution of population in Italy. 9. Describe the 
distribution in the Iberian Peninsula. 10. What is the average population -density of 
the Mediterranean shores? 11. What countries have mostly the dense and very dense 
grades of population? 12. What is the most striking contrast between the distribu- 
tion of population in Great Britain and the Iberian peninsula? 13. Compare the 
density of population in east and west Europe. 14. Compare the population-densities 
along the 40th and 50th parallels. 15. Where do the population -densities accord best 
with the data of the rainfall map? 16. Where is their least accordance? 17. About 
what is Danish life centered? 18. Compare the distribution of people and rainfall in 
the Turkish Empire? 19. What sort of agriculture prevails in Italy? 20. What 
appear from the map to be chief occupations in England? In northernmost Scotland? 

18. Distribution of Population in Asia. Fig. 3 
1. Name six groups of very dense population. 2. Locate and describe three 
areas of scanty population. 3. What American population group corresponds in its 
position in its continent to that of China? 4. What ones to Asia Minor and Palestine? 

5. Describe the distribution of population in Japan, India and China. 6. Compare 
the distribution of people and rainfall in China. (See map of annual rainfall.) 7. 
What grade of population occurs in the region of very heavy rain in India? Is that also 
true in other continents? 8. In general why are the inhabitated parts of Asia in the 
south and east? 9. Judging by density of population where is grazing most carried 
on? 

19. Distribution of Population in Africa. Fig 3 

1. Describe the areas of scanty population. 2. What does the map of annual 

rainfall show there? 3. Where is the most densely settled part of the continent? 4. 
Has it rain? How do the people manage to live there? 5. Why is west Madagascar 
scantily settled? 6. In general how well do the rain and population maps of Africa 
correspond? 7. To judge b3^ density of population what are the main occupations in 
Africa? 

20. Distribution of Population in South America. Fig 4 

1. How wide is South America's strip of thin to moderate population? (See 
dimensions of the meshes of the map net at the left border of the hemisphere.) 2. 

Where does the strip run? 3. What is its relation to the region of heaviest rainfall? 
4. Is this relation found anywhere else in the world? 5. In general what grade of 
rainfall is most often associated with considerable population? 6. What countries 
have strips of moderate population on the coast? 7. What countries have moderate 
population in the mountains? 

21. Distribution of People in Australia. Fig. 3 and Fig. 4 

1. What percentage of Australia has scanty population? 2. About how many 
square miles of inhabitated area has Australia? (See areas in the margin of the northern 
hemisphere. ) 

3. Does the rainfall map adequately explain the distribution of population? 4. In 
what respects does the distribution of population fail to agree with the rainfall map? 5. 
What are probable occupations of Australia's people? 



10 



Distribution of People 




GRADE of peopling 

Very dense 
Dense 
Moderate - 
Thin 
Scanty 



Fig. 3 






LEGEND 






SHADE 


PEOPLE 


TO ONE SQUARE MILE 


Black 


- 


250 or more 


Cross lined 


- . - 


125 to 250 


I/ines 


- 


26 to 125 


Dots 


- 


2jto 26 


Blank 


- 


less than 2i 



11 



IN THE World 




Fig. 4 



From data in Supan's Bevolkerung der Erde, 
Statesman's Year-Book and U. S. Census. 



12 




tig. 5 



3 20 10 10 20 30 40 50 




Fig. 6 



13 

22. Annual Rainfall, North America. Fig. 5 

1. What parts of the map show rain where no men live? 2. Why is this? 3. 
What meridian is a rainfall boundary in the United States? 4 Describe the rainfall of 
Canada. 5. Describe that of Mexico. 6. What is the shape of the scanty rain area? 

7. What percentage of the total area of the continent is made up by areas of light, 
moderate and heavy rain together? 

23. Annual Rainfall, Europe. Fig. 6 

1. Is there any region of considerable annual rain where the population is scanty? 

2. About what grade of population corresponds to the large area of scanty rain? 3. 
What grade of rainfall prevails in the parts of Europe most densely populated? 4. 
Compare the distribution of rainfall in the Scandinavian and Iberian peninsulas. 5. 
Does Europe's heav}' rainfall mostlj^ correspond with the denser population? 6. What 
is rainier, east or west Europe? 7. Which more populous? 8. What percentage of 
Europe has light to heavy rain? 

24. Annual Rainfall, Asia. Fig 7 

1. Where is there very heavy rain? 2. How much of Asia is dry? Where? 

3. Locate the light rains. 4. Describe the distribution of rainfall in India. 5. 
How well does it agree with the distribution of people? 6. Explain the distribution of 
population in connection with rainfall in the northernmost of the Philippine Islands 
(Luzon). 7. Compare the rainfall and population of eastern and western Turkey. 

8. Compare the rainfall and population densities of the East Indies in detail. 

25. Annual Rainfall, Africa. Fig, 7 

1. What percentage of Africa is dry? 2. Compare it with Europe in this respect. 
3. Where is Africa's heavy rain? 4. Compare the distribution of rainfall in northern- 
most and southernmost Africa with that of people. 5. Does Africa anywhere show 
heavier population where the rainfall is heavy? 6. Illustrate. 

26. Annual Rainfall, South America. Fig. 8 

1. Locate areas of very heavy rain. 2. How much of the continent is dry? 3. 
Describe the larger area of scanty rain. 4. What is the population grade along it? 
5. How does South America compare with other continents in the general supply of 
rainfall? 6. What four countries have each four grades of rainfall? 7. Describe the 
rainfall of the Argentine Republic and Chile. 

27. Australia, Annual Rainfall. Fig. 7 and Fig. 8 

1. What proportion of Australia is dry? Where? 2. Where are the very heavy 
rains'" 3. How does Australia compare with other continents in raininess? 4. 
Australia and the United States have about the same area: how do their rainy areas 
compare? 5. Which is rainier: New Zealand, Tasmania or Victoria? 

28. The student who has worked his way to this point will see the great control over 
man and his occupations that is exercised by rainfall. We shall now set forth the chief 
principles on which the distribution of rain depends. This involves a brief study of 
climate. 



14 



Annual Rainfall of the 




SHADE RAINFALL 

Black - Very Heavy 

Ruled lines Heavy 

Dots - Light 

Blank - Scant 



Fig 7 
LEGEND 

DETAILS 

An annual rainfall, including melted snow, of over 80 inches 
An annual fall of from 40 to 80 inches. 
An annual fall of from 20 to 40 inches. 
Less than twenty inches in the year. 



World (includes melted snow) 



15 



Fig. 8 

After Herbertson. 

In the blank areas agriculture is hardly possible without irrigation. Within them lie all the 
world's deserts. 



16 

CLIMATE 

29. It is important for teaching to recognize that climate is an abstraction, an ideal 
derived from the reality — weather. What is with us today is weather. It will be weather 
tomorrow that will affect us then. Only by examination of a long review of past weather 
can we come to any conception of the climate in which we have lived. The local weather 
thus becomes the appropriate point of attack for the study ot climate. The daily weather 
map enables us to extend the area of observation over most of North America, and becomes 
our most effective single means of instruction in all that pertains to climate. 

30. Both climate and weather reside in the lower air. Events above may be very 

different, indeed they commonly are. The conditions and changes of the upper air are of 

great interest to the student of weather, as helping us to understand what goes on below, 

but the events of our weather occur where we pass our lives, at the bottom of the ocean of 

air. 

The conditions of the lower atmosphere that concern us in this study are chiefly : 

Temperature, 

Pressure (Air good and bracing or muggy and oppressive) , 

Motion (Winds), 

The Presence and Condition of Water (Rain, clouds, dew and water vapor). 



Temperature of the Lower Air 

3.. How does it appear to you that this weather element ranks in importance for us? 
Does it matter more or less than rain? 

You will henceforth observe each morning at as early an hour as you are in the habit 
of going out of doors, how the temperature compares with that of the day before. It 
should not be supposed that the reading of the thermometer replaces this exercise for the 
student. It is perfectly possible to read the thermometer and record its indication in the 
book without ever thinking what it means . It is desired that the student come to class 
with a mind active with regard to the weather. The daily consideration of the question 
whether it is warmer, or cooler than the day before, or whether the temperature is not 
perceptibly different, will be found useful. A sufficient record is one of the words, 
"warmer," "colder," or "stationary." Any doubt is to be covered by the use of the 
word "stationary." 

32. It will appear very soon that the characteristic of our temperature is change — 
change through the day, change through the year, and change from day to day, apparently 
regardless of seasons. In what follows we look for the causes of this changeability. 

EXERCISE 1. — Temperature of Ground, Air and Water. A — Summer 

33. On a cloudless day take the temperature of some dirt that has been dried and 
some water in a pail, which have been exposed to the sun and air for equal lengths of time. 
The dirt and water should be set out early in the morning, and may remain out all night, 
if necessary. Make several readings of the thermometer each time, so that you may be 
sure of the accuracy of your results. In taking temperature in the sun, the bulb of the 
thermometer is to be placed in the loose surface dirt, or just beneath the surface of the 
water on which the sun has been shining. During the measure, be sure the thermometer 
bulb is shaded. As the shaded ground may cool off some during the observation, try a 
fresh place when the temperature ceases to rise. Always keep onlookers from shading 
ground or water, the temperature of which is to be taken. Note the time of the observa- 
tion. Air temperatures will be given in class. 



17 



Everyone should make observations as early in the morning and as late in the after- 
noon as possible and about half the class at noon, the other half at one. 

Make a neat, clean record of the temperatures, similar to the following: 

Temperatures 



Reading 


Time 


Ground 


Water 


Air 




Morning — 
Noon — 
1 O'Clock- 
Afternoon — 













1. Which heats up more rapidl}', the ground or water? 2. Do either get as hot at 
one as at noon? 3. Which cools off faster? 4. Which gets hotter? 

B-Winter 

When the snow is on the ground it is desirable to take snow temperatures. Students 
will make a series of such observations on any bright day in winter, when the ground is 
snow covered and the sun is shining on the snow to be studied. Make such observations 
at about 8 a. m., 10 a. m., noon, 2 p. m., and 4 p. m. or, as many of those hours as possi- 
ble. 1. Does the temperature of the snow ever vary? 2. How warm can it become? 3. 
How cold? 4. If you find variation, what is the cause? 

34. Physically the heat of the air consists in the rapidity of vibration of its particles; 
the faster they go the hotter the air. So too, of the ground, its heat consists of the rapidity 
of the vibration of its particles. Heat is communicated from one body to another in two 
ways, (l) by conduction, when the bodies are very near together, (2) by radiation at all 
sorts of distances. Heat comes to us, for instance, from the sun, as insolation, and heat is 
lost from the earth by radiation. It is believed that it travels away not as heat but as 
vibrations of all pervading ether*, which occupies not merely space but extends through 
all gasts and even some other bodies. The insolation then comes to us from the sun as 
vibrations of the ether which do not much heat the air in passing through it, as we may see 
when it warms pleasantly a south wall on a still winter day -after passing through very cold 
air. So the radiation from the earth into the upper air and space is by the same sort of 
vibrations of the ether, which do not materially warm the air in passing through. Conduc- 
tion, on the other hand, is illustrated by the warming of the air from the ground on 
which it rests. The ground being warmer than the air, its particles are vibrating faster 
than are those of the air. They are therefore supposed to hurry the adjacent air particles 
along in their swings until these too go more nearly at the same rate as the earth particles. 
Of course in doing this they lose some of their own speed and the result is a cooler earth 
as well as a warmer air. In usual language we say heat has been conducted from the 
ground to the air. And all the time that the lower air is being warmed by conduction, 
heat is radiating away from the ground through it to be lost in space, without much effect 
on the air on the way. For conduction one body must be warmer than the other, but 
radiation goes on all the time from cold bodies as well as hot, though its amount is propor- 
tional to the temperature. A hot body radiates more heat than a cold one. And so 
summer and winter, day and night, in cold and heat alike, heat is radiating away from the 
earth, just as on all clear days insolation comes to the earth through warm air or cold. 

*L0DGB,— The ^ther of Space. Nature, Jan. 14, 1909, p. 322. 



18 



35. The effects of the sun's rays are different according to the thing they fall on. 
Clear air allows them to pass through with little effect on it, so that a good deal Of insola- 
tion reaches the surface of the earth below. If this is land it heats up readily; if water, 
much less, since the rays pass through water somewhat as through air, although less 
freely. Anyone who has bathed on a sandy shore knows how strongly bits of stone or 
metal becomes heated in the sunshine, far more than the water ever does. Shallow waters 
attain a more agreeable temperature than deeper water, because the rays are able to pass 
through and warm the bottom, which warms the water in turn. The land surfaces are thus 
seen to be most sensible to the sun's warming power. For one thing the effects on 
solids are confined to the surface layers. At a very moderate depth below the surface of a 
rock exposed to the sunlight, no warming at all occurs. At a hot desert station in Tur- 
kestan, the mean temperature of the ground in the heat of the day, is 90°, but just before 
sunrise, 41°. Sixteen inches under ground the temperatures are 58.5° and 57.4° respec- 
tively, almost a uniform temperature from day to night. Most of the heat is concentrated 
in the five or six inches of depth just below the surface. In water the penetration is far 
greater. Some lakes in the temperate zone are warmed by the sun's rays as much as 40 
feet below the surface. The effect is therefore distributed through a mass of water so thick 
that each component layer is but little warmed. Moreover, a areat part of the effect of the 
sun's rays on the water surface is used in evaporation, without causing any sensible rise in 
temperature. Finally, water is a very hard thing to warm. From all of these causes it 
results that the ocean surface, or the surface of a deep lake rarely changes temperature by 
so much as 2° from day to night, while the land surfaces may show very large differences. 

36. Clean air is so much more transparent to insolation than water, that at times 
when the sun is high, three- fourths of the sun's heating power may become effective on 
the ground after passing through the whole depth of the air. Mainly, then, it is the dry 
land that is warmed by the sun. The most important point for the study of the weather is 
that the air is mostly warmed by the ground on which it rests and little by the rays of the 
sun that pass through it. The air temperatures never become so high as those of the 
ground. 

As the air gets most of its warmth from the ground, the upper air is always cold, with 
little variation from day to night. The daily range of temperature in the lower air near 
Boston, is in the mean 9°. By sending up kites with self-recording thermometers 
attached, it is learned that the range at 3000 feet elevation above is less than 1°. The 
1000 -foot Eiffel tower at Paris showed considerably less difference between day and night 
temperatures at the top than near the ground, an observation that is corroborated by nu- 
merous observations in different parts of the world. 

37. August 14, 1898, the following temperatures were 
noted at Askabad, in southern Turkestan, in the air, and on 
the surface of the ground, a fine, dry clay. The conditions 
are those of the desert, and the temperatures high. The sun 
set that day at 6:30 p. m. 1. How much warmer did the 
ground get than the air? 2. When did the ground get warm- 
est? 3. What was the range of temperatures on the surface 
of the ground that day? 4. In the air? It will be noticed 
that neither ground nor air was warmest at noon. The curve 
here given (Fig. 9) reproduces some of the temperatures of 
the table, the horizontal lines representing time, and the vertical ones temperature, each 
observation being represented by a dot. Thus the dot on the 10 o'clock line is at 92°, on 
the 12 o'clock line at 102°, as in the table. 



Ho 


ur 


Air 


Ground 


A.M. 


8 


82° 


91° 




10 


92 


137 




12 


102 


158 


P.M. 


2 


103 


160 




4 


106 


150 




6 


101 


129 




8 


87 


95 




10 


86 


88 




12 


86 


81 


A.M. 


2 


86 


80 




4 


S3 


80 




6 


81 


79 



19 













Nool 












































8 


9 


1 


1 


1 1 


2 1 


2 


3 


4 


5 


6 


7 


8 


9 


ID 


1 


1 1 


2 1 


2 


3 


4 


5 


6 


7 




10 

















































1 


oo 


^ 


^ 






9 







> 


^ 
















\ 


\ 
























90 


fl 







^ 




































. 









an 












7 



















































70 























































Fig. 9. Temperature, Askabad, August M, 1898 



EXERCISE 2.— Askabad Temperature Curves 



38. In Fig. 9 is drawn one of the two temperature curves for which data are given. 
Can you tell which one? Draw in the other one from the data, letting one square count 
horizontally for one hour, vertically for 10°. 

1. Which reaches its maximum temperature first, the ground or the air? 2. At what 
time in the afternoon do they both have the same temperature? 3. After that time, which 
radiates its heat more rapidly? 4. How great is the range of temperature of the ground? 
5. How great that of the air? 6. How great is it in this region at the same season of the 
year? (See air temperatures in Ex. 3 for Ypsilanti.) 7. In what region of the world 
is Turkestan, and what kind of a climate does it have? 8. In what way does that explain 
the extreme temperatures recorded? 9. Name some other region where the climatic condi- 
tions are similar, and where you would expect similar extremes. 

39. In general the heat received by the ground depends on the height of the sun in 
the sky. It is greater, therefore, at noon than in the morning, greater in summer than in 
winter, and greatest in the tropics where the sun at times stands overhead. Let the page 
of this book represent the surface of a town or city, as the book lies flat open on the table. 
If the sun should shine right down on it from above, the bundle of rays that touch the page 

would be as thick through as the page 
is wide. If, however, the sun shines on 
the page from a point little above the 
horizon, a very thin bundle, containing 
a few rays and little heat, spreads over 
the same surface. Thus the thick bundle 
of noon rays s s' (Fig. 10) renders much 
more heat to the surface in which A B is 
a line than the thin bundle of slanting 
rays s" s" ; although each bundle is just 
wide enough to shine on the whole 
width of AB. 

In the United States, of course, the sun is never overhead but its heating power is 
greater in proportion as it gets higher in the sky. 

40. Working against this warming by the sun is the radiation by which the earth 
is always giving up heat, even while the sun is shining down upon it; most at the season 
when the earth is warm, but always in considerable amount. Whether the earth is gaining 




Fig. 10 



2d 

bt losing heat at any moment, depends on the relation of this radiation to insolation, ot 
solar warming. From the tables of temperature given, and from the January temperatures 
at Ypsilanti, we learn that the maximum or greatest heat does not occur until afternoon. 

1. While the earth is warming which must always be greater, insolation or radiation? 
2. If it is warmer at one than at noon, is insolation or radiation greater between those 
hours? 3. When is insolation greatest? 4. What change is it undergoing from noon to 
one? 5. How can a diminishing insolation still cause the earth to get warmer? (See l). 
6. What is the relation of insolation and radiation at the moment of greatest heat? 7. 
Before that moment? after? 8. Why is it not hottest at noon? At Askabad the ground 
was steadily gaining heat as the sun rose higher in the sky. If there was heat lost by 
radiation, it was less than was received from the sun at the same time. At 2 p. m. the 
maximum temperature of 160° was attained. From that moment we must regard the loss 
by radiation as greater than the insolation, and the ground cooled off steadily. 

The same effect is observable in the air temperatures, and here the maximum comes 
still later. 







Ypsilanti 


41° N 


53° W. 


1904 


Hour 


AirT. 


AirT. 


Water T. 


July 9 





67° 


71° 


72° 




4 


63 


69 


72 




8 


68 


72 


70 




Noon 


77 


70 


72.5 




4 


81 


70 


72.5 




8 


72 


63 


74 




12 


69 


61 


72.5 


July 10 






42 N. 
61 


45 W. 
72.5 


.--._ 


"""69°""' 




4 


63 


60 


67 




8 


68 


62 


69 




Noon 


77 


61.5 


66 




4 


81 


60 


68 




8 


72 


56 


67' 




12 


69 


56 


68 



EXERCISE 3. — Diurnal Temperature Curves at Ypsilanti and on the Atlantic Ocean 

41. Construct curves by these data, 
placing the long way of the page right and 
left and then counting each square of the 
quadrille paper vertically as one degree, 
horizontally as one hour. Make each 
curve continuous through the two days and 
place all on one diagram. Both days were 
clear. The observations in the last two 
columns were made on the steamer United 
States, moving east fifteen miles per hour. 
All large vessels crossing the ocean make 
such observations at these hours and record 
them in a ship's journal known as its "log. ' ' 
1. Locate the places in the atlas. 2. At which of the three places was the air 
warmer? 3. Why? 4. Where was the daily range of temperature greater? 5. How great? 
6. Do the Ypsilanti observations show the effect of the sunshine — say from 5 a. m. to 7 p. 
m.? 7. Do the air temperatures over the ocean show anything similar? Notice the 
behavior of the curve about five each morning and again at seven each night. If you 
draw a straight line along that whole curve for the air temperatures over the ocean in such 
a way that it runs as near as possible to all the temperature dots, you will be able to detect 
a sun effect each day. The ship is getting into cooler and cooler air but during daylight 
the cooling is checked. 8. Can you find any sun effect in the curves for the temperature of 
the water? 9. Suppose the United States were passing across bands of cooler and 
warmer water, some 50, some 300 miles wide as the steamer travels. Would that explain 
the water temperatures? 10. Look up Gulf Stream in the Encyclopedia to learn more 
about this. 

42. The curves of paragraph 41 show how moderate are the changes in the tempera- 
ture of the ocean air in our latitudes from day to night. So too the summer air out there 
is little warmer than that of winter. The west winds, that are the commonest of all the 
winds in our zone, blow this mild ocean air over the western lands of Europe and give 



21 

them their mild climate, much less hot in summer and less cold in winter than in eastern 
Europe in the same latitudes. Central Ireland has mean temperatures of 46° and 60° in 
February and August respectively, as compared with 20° and 68° in the same latitude in 
Russia. The Atlantic waters, on the Irish coast, have temperatures at the same seasons, 
of 50° and 60°. Is that warm water? 

EXERCISE 4 

43. Draw four temperature curves from the data in the following table, which gives 
average hourly temperatures for summer and winter months at Ypsilanti and Cuzco. 

Put all four curves on a single diagram with one square of the quadrille paper for 2° 
vertically and one hour horizontally. 

1. Where is Cuzco? 2. In what lati- 
tude? 3. At what altitude? 4. Does the 
curve for the temperate zone represent the more 
temperate weather? 5. What surprising fact 
with regard to summer and winter day tempera - 
atures do these curves show? 6. Cuzco has 
distinct wet and dry seasons, with 34 and 63 
per cent respectively of clear sky. That will 
help to answer the questions that follow. The 
effect of clouds is (l) to prevent the sun's rays 
from reaching the ground and (2) to hinder the 
earth's heat from radiating away. That of 
course would have an effect on the day and 
night temperatures at any place. Thus in the table of hourly temperatures at Ypsilanti 
for January the 29th was clear and the 30th cloudy. 7. What would be the effect of 

clouds on the day part of the curve? 8. What on the night part? 9. What on the 
daily range of temperature? 10. When has Cuzco less daily range? 11. When has 

Cuzco clouds and rain? 12. Is January or July summer at Cuzco? 13. Which 
curve should run among higher temperatures? 14. When does it run higher? Why? 
(See 7 and 8). 15. Why do the nights differ more than the days? 

EXERCISE 5.— Curves for Clear and Cloudy Days 

44. Select from the data at pages 22 and 23, one day at each place that from the 
resemblance of the data to those for Ypsilanti air in Exercise 3, you think may be clear 
days, and construct the curves, labeling them with the date. 

Select one day from each place that from its differences from the type of July 9, seems 
to be a cloudy day, and construct its temperature curve. State briefly the considerations 
that govern you in making the selection. 

EXERCISE 6 

45. It will help toward clear thought if, in speaking of this afternoon maximum of 
temperature, we refer its time, not to noon, but to the thing which fixes noon; the sun's 
height in the sky. 

1. When in the day — in terms of the sun's height in the sky — is it hottest? AFTER 
THE MOMENT OF HIGHEST SUN! The sun is highest of all the year for us on 





Cuzco 


Ypsilanti 


Jan. 


July 


Jan. 


July 





48 


i% 


14 


65 


2 


47 


36 


14 


64 


4 


46 


35 


14 


62 


6 


46 


34 


14 


65 


8 


49 


41 


14 


68 


10 


55 


51 


17 


74 


N 


60 


57 


20 


77 


2 


59 


59 


21 


79 


4 


56 


56 


20 


77 


6 


54 


49 


18 


75 


8 


51 


44 


16 


72 


10 


49 


40 


15 


67 





48 


38 


14 


65 



The Gulf Stream, J. B. Pillsbury, Washington, '91. Chart at page 507. 



22 

June 21st, the summer solstice. 2. When in the year, in similar terms, is it hottest? I,et 
us now construct annual temperature curves for Cuzco and Ypsilanti counting one square 
of the quadrille paper vertically for a degree and two squares horizontally for a month. 
We shall use the mean or average temperature of the whole month and consider the date 
that of the middle of the month. 



Cuzco Ypsilanti 



January 51 5 24 5 

February 51 9 23 

March 52.2 32.6 

April 51.3 46 3 

May 49.6 56.8 

June 46 6 66 1 

July 45.0 69. S 

August 48.1 67.7 

September... 49.9 61.3 

October 51.2 49.4 

November 51.8 36 8 

December 51.2 27.1 



3. At Ypsilanti at what date in the year is it hottest? 
4. At what date is the sun highest? 5. What is the time of 
greatest heat in terms of the time of high sun? The Cuzco 
curve is peculiar. 6. When does it appear to be hottest at 
Cuzco? Hottest must here be taken to mean hotter than 
just before and just afterward. In that sense could there 
be two hottest moments? 7. How often is the sun high at 
Cuzco? 8. At what seasons, as we call them? 9. At that 
time at what point in the Cuzco sky is the sun? 10. 
When is it hottest at Cuzco, with respect to the high sun? 

11. Why are not the two hot moments six months apart? The sun crosses the Cuzco 

zenith on the 12th of February and 30th of October. 

46. The student should now add to his daily weather record the direction of the 
wind and the force of the wind as expressed in the Hazen wind scale. 

Force of the Wind. 

0— Calm 

1— Moves leaves of trees. • 

2 - Moves branches. 

3 — Sways branches, lifts dust. 

4— Sways trees, lifts twigs from ground. 

5 — Breaks small branches. 

6 — Destroys everything. Hurricane. 

47. The temperature of a day may be ascertained by averaging the observations of a 
thermometer read every hour, but so many readings are very troublesome to make. Where 
the expense ($25) does not prevent, an instrument like our thermograph gives good results 
with very moderate care. A much less expensive instrument that is little trouble to use is 
the maximum and minimum thermometer, to be seen in our laboratory and explained at 
page 60 of Davis' Meteorology. By referring to the temperatures given in 48, we readily 
make out the relation of the half sum of maximum and minimum temperatures to the mean 
of the twenty four hourly observations. On January 1st, the minimum was 12 , maximum 
24°, their half sum, 12 + 24 - 2 = 18. The mean of the twenty-four hour values is 19°. 1. 
On the second the half sum is 4° to a mean of 7°. 3. 1. How is it on the third, fourth, 
fifth, and sixth? 2. Make the same comparison for the mean values at the bottom of the 
page in both 20 and 21. The two numbers are usually within a degree of each other. 
For very many places in the world this is our only means of getting the temperatures. 
Those for Ypsilanti in 45 result from 15 years of such observations. 



23 



48. HOURLY TEMPERATURES AT YPSILANTI, MICHIGAN 

JANUARY, 1904 





MORNING 


AFTERNOON 




Jan. 


1 


2 


3 


4 


5| 6 1 7 1 8 


9 


10 


1 111 N 


1 1 


2| 3 1 


4 1 5 1 6 1 7 1 8 9 1 10 1 11 1 Mt. 


Mean 


1 


23 


24 


24 


24 


22 


22 


21 


19 


18 


20 


21 


22 


22 


22 


22 


21 


17 


16 


16 


15 


13 


12 


12 


12 


i9Ti 


2 


12 


12 


11 


10 


10 


9 


8 


.7 


7 


7 


7 


8 


9 


10 


10 


10 


10 


9 


8 


6 


2 





-2 


-4 


7 3 


3 


-4 


-6 


-7 


-7 


-8 


-9 


-8 


-7 


-5 





3 


5 


7 


9 


10 


10 


8 


7 


5 


5 


6 


6 


5 


5 


1.2 


4 


4 


2 


2 


1 





""i. 


-3 


-3 





4 


9 


11 


11 


10 


10 


10 


8 


7 


4 


2 


1 


-1 


-2 


-4 


3.4 


5 


-6 


-6 


-6 


-7 


-7 


-6 


-4 


-1 


2 


6 


9 


11 


12 


18 


16 


14 


14 


14 


14 


13 


13 


16 


16 


14 


6.6 


6 


14 


12 


12 


13 


14 


16 


17 


19 


20 


22 


24 


24 


25 


28 


28 


27 


25 


24 


23 


22 


23 


24 


24 


24 


21.0 


7 


24 


25 


25 


24 


24 


24 


21 


20 


20 


20 


21 


?4 


24 


25 


26 


28 


29 


29 


29 


29 


31 


31 


31 


31 


25.6 


8 


32 


33 


34 


34 


34 


34 


35 


35 


34 


35 


35 


36 


36 


23 


33 


33 


32 


31 


31 


30 


29 


27 


26 


24 


32.3 


9 


24 


22 


22 


23 


22 


22 


21 


21 


22 


22 


23 


24 


24 


24 


24 


23 


22 


22 


22 


22 


22 


21 


20 


14 


22.0 


10 


12 


10 


6 


4 


4 


4 


6 


9 


11 


13 


16 


18 


19 


20 


20 


20 


20 


20 


20 


20 


20 


20 


20 


20 


14 7 


11 


20 


20 


19 


19 


18 


18 


17 


15 


13 


12 


14 


15 


17 


18 


17 


17 


17 


18 


18 


19 


19 


19 


20 


20 


17.5 


12 


19 


20 


20 


21 


21 


22 


22 


22 


22 


23 


24 


24 


25 


25 


25 


25 


25 


25 


25 


26 


26 


25 


24 


24 


23.3 


13 


20 


22 


24 


24 


25 


26 


26 


26 


26 


26 


26 


27 


27 


26 


25 


24 


23 


23 


24 


24 


24 


22 


22 


21 


24.3 


14 


23 


24 


24 


24 


23 


23 


20 


20 


20 


21 


22 


22 


22 


22 


23 


23 


22 


22 


22 


22 


21 


20 


20 


18 


21 8 


15 


18 


18 


19 


18 


16 


17 


18 


17 


18 


21 


23 


25 


25 


25 


24 


24 


24 


24 


23 


22 


22 


22 


22 


22 


21.1 


16 


22 


22 


23 


23 


23 


24 


27 


28 


30 


31 


31 


30 


27 


23 


22 


20 


19 


18 


16 


15 


14 


13 


12 


12 


21.9 


17 


10 


11 


12 


13 


13 


13 


12 


11 


11 


11 


11 


13 


14 


14 


14 


14 


12 


12 


12 


11 


10 


11 


10 


7 


11 8 


18 


6 


5 


4 


4 


4 


4 


4 


4 


4 


8 


10 


13 


13 


12 


11 


8 


7 


5 


4 


2 


2 


2 


3 


4 


60 


19 


4 


6 


7 


7 


7 


8 


8 


9 


10 


12 


14 


18 


21 


25 


28 


30 


32 


34 


35 


36 


36 


36 


35 


36 


20.6 


20 


36 


36 


36 


36 


36 


36 


36 


36 


36 


36 


37 


36 


36 


34 


34 


33 


32 


32 


32 


32 


32 


32 


32 


32 


34.4 


21 


32 


32 


32 


32 


32 


31 


30 


30 


31 


32 


32 


32 


32 


33 


33 


32 


32 


32 


32 


31 


31 


31 


30 


30 


31.5 


22 


31 


32 


32 


32 


34 


34 


34 


34 


33 


34 


34 


32 


32 


32 


32 


31 


30 


28 


28 


28 


28 


28 


28 


28 


31.2 


23 


28 


27 


26 


26 


26 


26 


26 


26 


27 


28 


28 


28 


28 


28 


26 


25 


22 


20 


17 


14 


11 


10 


10 


10 


22.6 


24 


6 


5 


4 


3 


1 





-1 


-1 





2 


4 


5 


5 


5 


5 


2 


-1 


-3 


-4 


-5 


-6 


-6 


-6 


-6 


0.3 


25 


-7 


-7 


_7 


-7 


-7 


-6 


-6 


-5 


-4 


-1 


2 


4 


7 


8 


7 


6 


6 


6 


5 


4 


4 


4 


4 


4 


0.6 


26 


4 


4 


4 


4 


5 


6 


6 


7 


8 


10 


10 


11 


12 


12 


14 


13 


11 


10 


9 


8 


9 


9 


7 


6 


8.3 


27 


6 


6 


6 


5 


4 


4 


3 








3 


6 


9 


10 


10 


10 


10 


8 


5 


3 


2 


1 








1 


4.7 


28 


3 


4 


4 


4 


4 


4 


4 


3 


5 


7 


10 


12 


14 


15 


17 


17 


15 


12 


9 


6 


5 


4 


5 


4 


7.8 


29 


4 


6 


6 


5 


5 


6 


6 


7 


10 


15 


17 


18 


20 


21 


21 


19 


16 


11 


12 


7 


1 


-1 


-2 


-2 


9.5 


30 


-2 


-2 


-1 


3 


5 


7 


9 


12 


17 


22 


25 


26 


28 


29 


27 


26 


26 


27 


27 


27 


28 


27 


26 


26 


18.5 


31 


25 
14.2 


25 

14.3 


24 
14.2 


25 
14.2 


26 
14.1 


26 

14 3 


26 

14.2 


28 

14.5 


28 
15.-3 


28 

17.1 


28 
18 1 


28 
19.7 


27 


25 

20.7 


24 
20 6 


22 
19.9 


22 

18.8 


20 
18.1 


20 
17.5 


18 
16.5 


17 
16.0 


16 
15.4 


16 


16 


23.3 


Mean 


20.4 


15.1 14.5 


16.6 



u 



49. HOURLY TEMPERATURES AT HAVANA, CUBA 

JANUARY, 1904 



1 MORNING 


AFTERNOON 




Jan. 


1 1 2\ 3| 4| 5| 6| 7| 81 9|10|11| N 


1 1 2 


3 1 4 1 5 1 6 


7 18 19 


10 1 11 1 Mt. 


Mean 


1 


64 


64 


63 


63 


63 


63 


62 


64 


67 


68 


70 


72 


73 


73 


73 


73 


72 


70 


69 


68 


67 


66 


65 


65 


67.4 


2 


64 


64 


63 


63 


63 


61 


61 


66 


70 


73 


75 


76 


76 


76 


77 


76 


74 


72 


71 


70 


69 


68 


67 


66 


69.2 


3 


64 


64 


64 


63 


62 


63 


64 


68 


73 


76 


78 


76 


76 


75 


75 


75 


75 


74 


74 


74 


72 


72 


72 


71 


70.8 


4 


71 


71 


70 


70 


70 


70 


71 


70 


71 


71 


71 


72 


72 


73 


73 


74 


72 


71 


71 


71 


71 


70 


69 


69 


71.0 


5 


70 


70 


70 


69 


68 


67 


67 


67 


68 


69 


70 


70 


70 


68 


67 


67 


67 


66 


65 


66 


66 


67 


66 


66 


67.8 


6 


65 


65 


66 


68 


68 


67 


67 


65 


68 


72, 


74 


73 


73 


73 


73 


73 


72 


70 


68 


67 


66 


65 


64 


64 


68.6 


7 


63 


62 


62 


62 


61 


61 


61 


63 


67 


71 


72 


73 


74 


76 


77 


75 


74 


74 


73 


70 


69 


67 


67 


67 


68.4 


8 


67 


71 


71 


72 


72 


72 


71 


70 


70 


71 


71 


72 


69 


70 


70 


70 


70 


68 


68 


67 


67 


67 


66 


67 


69.5 


9 


66 


66 


65 


65 


64 


64 


64 


64 


66 


69 


70 


70 


72 


71 


70 


71 


70 


68 


67 


65 


64 


62 


61 


60 


66.4 


10 


60 


60 


60 


58 


57 


57 


58 


60 


64 


70 


73 


74 


75 


78 


77 


77 


77 


75 


74 


70 


70 


70 


70 


70 


68.1 


n 


68 


68 


69 


68 


68 


68 


68 


68 


72 


75 


77 


79 


81 


77 


78 


80 


79 


77 


74 


72 


71 


71 


71 


70 


72.9 


12 


70 


70 


69 


69 


69 


67 


67 


70 


74 


78 


80 


80 


79 


79 


78 


77 


77 


76 


74 


72 


71 


70 


69 


68 


73.0 


13 


67 


66 


65 


66 


65 


65 


65 


66 


68 


74 


76 


77 


78 


78. 


78 


78 


77 


77 


74 


72 


71 


69 


69 


69 


71.2 


14 


69 


67 


66 


66 


66 


66 


66 


66 


67 


69 


68 


67 


66 


66 


65 


65 


64 


64 


63 


63 


62 


61 


61 


60 


65.1 


15 


60 


61 


61 


60 


61 


61 


61 


65 


66 


67 


68 


68 


69 


70 


70 


69 


69 


68 


66 


65 


64 


63 


60 


60 


64.7 


16 


59 


60 


60 


60 


60 


60 


61 


63 


67 


70 


70 


7i 


73 


73 


74 


74 


74 


72 


69 


68 


67 


66 


65 


64 


66.8 


17 


64 


64 


64 


63 


62 


62 


61 


62 


66 


73 


74 


73 


73 


74 


75 


74 


74 


73 


72 


71 


70 


68 


66 


65 


68.5 


18 


64 


63 


62 


61 


60 


60 


60 


63 


66 


71 


70 


73 


74 


74 


74 


74 


74 


72 


71 


71 


72 


71 


70 


68 


68 3 


19 


68 


67 


68 


68 


69 


69 


69 


71 


71 


74 


75 


74 


74 


74 


73 


73 


73 


72 


71 


71 


72 


70 


71 


70 


71.1 


20 


67 


68 


70 


69 


68 


67 


68 


68 


69 


72 


73 


74 


74 


75 


75 


74 


74 


72 


71 


70 


70 


69 


69 


68 


70 6 


21 


66 


65 


65 


66 


65 


63 


63 


64 


68 


71 


74 


76 


76 


78 


78 


78 


79 


78 


75 


74 


74 


71 


71 


68 


71.1 


22 


67 


67 


68 


66 


67 


66 


65 


70 


73 


74 


75 


78 


79 


80 


81 


80 


79 


77 


76 


75 


74 


74 


73 


74 


73.3 


23 


74 


73 


72 


71 


71 


71 


70 


71 


71 


71 


73 


75 


78 


79 


80 


80 


79 


78 


77 


76 


75 


74 


74 


73 


74.4 


24 


73 


73 


72 


72 


70 


70 


68 


66 


63 


64 


64 


64 


65 


63 


63 


62 


65 


63 


64 


65 


65 


66 


66 


66 


66 3 


25 


66 


67 


66 


66 


67 


69 


68 


68 


69 


70 


73 


74 


76 


76 


77 


77 


77 


76 


74 


74 


73 


72 


71 


70 


71.5 


26 


69 


69 


69 


69 


69 


68 


67 


70 


71 


74 


75 


79 


80 


78 


76 


73 


73 


72 


72 


70 


70 


70 


70 


69 


718 


27 


69 


69 


68 


67 


67 


66 


65 


66 


68 


74 


77 


76 


77 


77 


77 


76 


76 


77 


76 


75 


74 


72 


71 


71 


72.1 


28 


70 


68 


67 


68 


67 


67 


67 


68 


69 


73 


74 


76 


78 


79 


78 


79 


78 


77 


75 


74 


73 


71 


71 


71 


72.4 


29 


70 


70 


69 


68 


68 


66 


66 


69 


72 


76 


78 


79 


82 


84 


84 


83 


82 


79 


76 


75 


74 


73 


73 


71 


74.4 


30 


71 


71 


71 


70 


70 


69 


69 


70 


71 


71 


72 


73 


73 


73 


74 


74 


73 


73 


73 


73 


71 


72 


72 


72 


71.7 


31 


72 


71 


69 


68 


68 


67 


66 


66 


71 


76 


77 


79 


80 


82 


83 


83 


82 


80 


77 


74 


73 


72 


71 


71 


74 1 


Mean 


67.2 


67.0 


66.7 


66.4 


66.0 


65.6 


65.4 


66.6 


68.9 


71.9 


73.1 


74.0 


74.7 


74.9 


75.0 


74.7 


74.2 


72.9 


71.6 


70.6 


69.8 


69.0 


68.4 


67.9 


70 1 



EXERCISE 7.— Heat used in Evaporating Water 



Hour 


April 16 


April 17 





28° 


25° 


2 


24 


24 


4 


20 


24 


6 


20 


26 


8 


23 


34 


10 


26 


39 


Noon 


28 


44 


2 


30 


47 


4 


30 


47 


6 


29 


44 


8 


28 


40 


10 


27 


38 


12 


25 


36 



50. Plot curves for Ypsilanti. April 16: Sky 
clear, wind west, velocity 1, ground covered with 1 
inch of snow. April 17, sky clear, wind northwest, 
velocity 1, ground bare all day. 

Each square on the quadrille ruled paper verti- 
cally equals 2°, horizontally, 1 hour. Explain the 
difference in the temperature for the two days as 
shown by the curves. 



25 

1. What was the maximum temperature the first day? 2. The minimum? 3. The 
range? 4. What the maximum the second day? 5. The minimum? 6. The range? 7. 
Is there anything about snow to keep it from getting hotter than 30°? 8. Why didn't it 
get warmer on the 16th? 9. What is the maximum temperature for days with snow on 
the ground? Of course a strong wind might bring warm air or cold air from a distance. 
We are supposing there is little wind and that the changes in temperature are those due to 
local causes. 10. What work had the insolation to do on the 17th? 11. What additional 
work on the 16th? 

Air Tends to Expand when Heated, and to Yield to Pressure when Cooled 

51. Why does air expand when heated? The particles of air are believed to be in 
rapid motion, vibrating in some way back and forth. The faster the vibration, the hotter 
the air. The particles are of course too small to see with the most powerful microscope ; 
the distances through which they move are doubtless also very small, and the speed of the 
motion very great, even for bodies at ordinary temperatures. That is our general concep- 
tion of warm bodies. If the vibrations are more rapid when the air is warmer, to heat a 
mass of air is to set its particles vibrating faster, but it is also natural, therefore, to think 
of these particles as pounding on the walls that confine them, and demanding more space 
and taking it, if not resisted by a force too great. This should not be regarded as an 
explanation why air expands when heated, but rather as pointing out that the expansion is 
reasonably accordant with our whole notion of heat. Similarly when air is cooled, its par- 
ticles are thought of as vibrating more slowly, and moving through smaller spaces. They 
may be supposed, therefore, to strike less vigorously against the side of the containing 
vessel. If under pressure, it is intelligible that such air should yield to the pressure and 
contract. Much confusion in the theory of the winds arises from the loose doctrine that 
warmed air rises and cooled air sinks. A good test between this and the view stated at the 
head of this paragraph is to isolate some air, warm it and cool it and note its behavior. 

EXERCISE 8 

52. Apparatus: A flask fitted with a rubber stopper, having a single hole through 
which a long glass tube is fitted, and a glass of water. 

Invert the flask, allowing the end of the tube to dip into the water. Note the level of 
the water in the glass and in the tube. Now warm the flask with both hands ; note and 
record what happens. What would have happened had there been no outlet? Carrying 
the apparatus out of doors or to the open window, causes what to happen? What would 
have happened had there been no outlet? Drawings should be made of the apparatus, 
showing the stand of water in glass and tube in all three stages of the experiment. What 
is your opinion of the sufficiency of the statement that warm air rises? Did it in this 
case? That cold air sinks? Did it? If warm air rises, why is not the upper air warmer 
than the lower? Is it? 

Where Air Expands Under Pressure and Does Work, it Loses Heat 

53. To demonstrate this, set up the apparatus as shown. The two flasks are 250 
cubic centimeter flasks each fitted with a thermometer to record temperature, the first 
tightly stoppered and the second connected to a U tube containing mercury. A scale 
mounted by the U tube serves to register any variation in the height of the mercury. The 
heat is very satisfactorily furnished by two candles of the same size. Be careful in setting 
up apparatus to get all connections air tight, and that the candles are of the same size and 



26 

mounted with the flame the same distance under the flasks (not less than four inches. ) 
After the apparatus has been carefully set up take the temperature, light the candles and 
record the temperatures in the two flasks every minute, also the height of the mercury in 
the U tube. Record it until no further variation in the height of the mercury occurs. 
Tabulate your results. Explain any difference in the temperatures noted in the two flasks. 
Suppose we could apply the heat from the combustion of a unit of fuel to warm a quart of 
air enclosed in a glass flask with a rubber stopper and tube dipping into mercury, as in 
the experiment. Let us further suppose that no heat is lost, that the air expands with the 
heat, pushing the mercury down in the tube, and also becomes one degree warmer. Now 
if the experiment could be repeated with all the quantities and conditions the same, except 
that the quart of air was contained in a strong vessel that would not let it expand, the 
result would be that the air would rise in temperature more than one degree, although its 
original temperature was the same, the initial quantity of air the same, the original pres- 
sure the same, and the amount of heat used the same. The result may be stated thus: the 
amount of heat that somewhat warms air that is free to expand, will produce a greater rise 
in 'emperature in the same quantity of air confined. If less warming is produced upon air 
that expands, what becomes of the rest of the heat in this case? The answer is that it is 
used up in the work done. When the air in the flask expanded, it had to push the 
mercury up in the tube, and that was work. To do work energy is needed. The only 
energy at hand to do the work was the heat supplied, and whatever energy was devoted to 
expansion could not also appear as a rise in temperature. 

Air is Cooled by Expansion 

54. Now if the flask of air that was closed by the mercury in the U tube could be 
placed under the receiver of an air pump and some of the air pumped out of the receiver, 
the air within would expand, would push down the mercury in the near side of the tube 
and up, of course, in the other. This would be doing work, but we are not now supply- 
ing heat to do this work with. If the temperature of the air in the flask were noted before 
and after the experiment, what should we see? Energy that was just now occupied in 
what we might call heat work — moving the air particles back and forth at the rate proper 
for the temperature — has now been diverted to lift a little mercury against gravity. Only a 
part of it, therefore, is now engaged in heat work, or, we may say, the air has been cooled 
in expanding against pressure. If a quantity of air is compressed into a strong vessel and 
allowed to stand until it has taken the temperature of the room, it will suffer a distinct fall 
of temperature if allowed to expand under pressure, as in the previous experiment. In 
this case it has onlj"- its own heat to call on to do the work of expansion, and as soon as 
that is done the temperature falls. It appears, therefore, that not only does heat cause 
expansion, but that expansion taking place, as it usually does, against pressure, uses up 
heat and causes cooling. This must not be taken to mean that expanding air always falls 
perceptibly in temperature, the fall is only perceptible when no external heat is supplied to 
it, or not enough to do the work. When external heat is supplied, the temperature rises 
all the time the air expands. In thought only do we have a succession of events; first, the 
air warmed X plus y degrees ; second, the air, expanding, uses up some of its heat and 
cools through y degrees, with the final result of a rise in temperature of x degrees and an 
increase in volume. In reality heating and expansion are simultaneous. Some of the heat 
is applied to the heating, while the rest is used in the work of expansion. 

For the air that was not allowed to expand, all the energy supplied was applied to 
raising the temperature, which accordingly rose higher than that of the expanding air. 
This is simplj^ shown by experiment. 



27 

Air is Warmed by Compression 

55. On the other hand when air is compressed by the application of force, the energy 
used is transformed into heat and the air warmed. When gases are mechanically com- 
pressed, provision has to be made by the circulation of cold water or otherwise, to get rid 
of the heat generated. (Tyndall's Heat as a Mode of Motion, lecture I and III, may be 
read in this connection. 

Geographic Applications 

56. All of the layers of air in which the phenomena of the weather take place, are 
under pressure from the atmosphere above. If this pressure diminishes, the air expands, 
and is thereby cooled. Conversely, when the pressure increases, the air is compressed 
and warmed. As the winds move over the surface of the earth, at times they ascend and 
descend the slopes of the mountains. When they ascend they go nearer the surface of the 
ocean of air. In that case there is less air above them, so they are able to expand and lift 
the air above, which cools the winds because of the work done. In general, air That 
RISES EXPANDS AND COOLS. When the winds descend they go deeper below the surface of 
the ocean of air. As this puts more and more air above them, they yield to the increasing 
pressure, contract, and are warmed by this compression. In general again, air that 

SINKS IS COMPRESSED AND WARMED. 

Since the pressure of the atmosphere at various levels is pretty well known, it is possi- 
ble to calculate these changes of temperature due to ascent and descent of air. They 
amount to 5.2° per thousand feet and are known as adiabatic temperature changes. They 
apply only to air that rises and falls. A person climbing a thousand feet up on the side 
of a mountain would not find it 5.2° cooler above unless the air went up with him. It 
often occurs to^students at this point that these doctrines are contradictory. Descending 
air is compressed and warmed, but since warmth causes air to expand, it may seem as if 
the work of compression would be at once undone by the action of the heat generated. 
The diflSculty is apparent only. Heat does not cause expansion but a tendency to expand. 
Whether a gas expands or not depends on the pressure to which it is subjected. The 
descending air that is compressed by the weight of the air above cannot expand, since the 
fact of its compression proves that it is unable to resist this weight, so all of the heat is 
used to warm the air. 

It is often taught that cold, lofty mountains cool the warm winds that blow on them 
from oceans and thus make them drop their moisture as rain. We have seen that the 
cooling is really adiabatic cooling within the air itself and therefore not caused by the 
mountains. But observation at many observatories on mountains show higher tempera- 
tures there than kites reveal at the same height in the free air. Furthermore since the air 
is constantly flowing over the mountains today, tomorrow, next year, next century and for 
thousands and thousands of years it is evident that such enormous volumes of warm air 
must rather warm the mountain than be cooled by it, for the hugest mountain chain is of 
insignificant bulk beside such masses of air as that. 



28 



EXERCISE 9— Cold Aloft 

57. Calculate the diminution of temperature per thousand feet of ascent from the data 
in the following table. As an illustration of the method to be followed: Geneva is seen to 
be 2230 feet lower than Chamonix; this by the printed table. Also 9° warmer. In this 
case therefore it was found to be 9° cooler for an ascent of 2230 feet, how much is that 
for every 1000 feet? 



Pjlace 

Geneva 

Chamonix 

Pass (Col du Geant; 

Dodge City, Ks 

Dodge City, Ks 

Dodge City, Ks 

Dodge City, Ks 

Dodge City, Ks 

Dodge City. Ks 

Pierre, S. Dak 

Pierre, S. Dak 

Lansing, Mich 

Lansing, Mich 

Cleveland, O 

Cleveland, O 

Cleveland, O 

Cleveland, O 

Arlington, Va 

Arlington, Va 

Arlington, Va., 

Arlington, Va 



Time 



July 5-18, '88, Mean Values 
July 5-18, '88, Mean Values 
July 5 18, '88, Mean Values 



Station and Elevation i Temp. 



1312 feet 

3542 feet 

11152 feet 



73° 
64° 

37° 



KiTK Observations 



23, 
23, 

23, 
23, 



July 
July 
July 
July 
June 29, 
June 29, 

June 22, 
June 22, 



June 11, 
June II, 



June 12, 

June 12, 

June 26, 

June 26, 



98, 10 A. 



M. 



98, 



10 A. M. 



98, 2:10 P. M. 
98, 2:10 P. M. 
98, 
98, 



10 A. 
10 A. 



98, 11 A. 
98, 11 A. 



M. 
M. 

M. 

M. 



Ground 

Kite 

Ground 

Kite 

Ground 

Kite 



Ground 
Kite 



5795 
5419 

4477 

5492 



81° 

59° 

85 5° 

61° 

80° 

67° 



87° 
75.3° 



98, 
98, 



11 A. M. 
11 A. M. 



Ground 
Kite 



5351 



81° 
559 



98, 9 A. M. 

98, 9 A. M, 

98, 8:25 A. M. 

98, 8:25 A. M. 



Ground 
Kite 
Ground 
Kite 



5319 
3146 



79.5° 
58° 
76° 
65° 



May 12, 

May 12, 

June 14, 

June 14, 



98, 8:30 A. M. 

98, 8:30 A. M. 

98, 6 A. M. 

98, 6 A. M. 



Ground 
Kite 
Ground 
Kite 



8211 

2143 



67° 
44.5° 
77.5° 
72 4° 



Balloon Observations 



Mean of all times and places. 



9840 
16400 
32800 



19° 

3° 

-67° 



After computation of the rate of decrease per thousand feet of ascent in each individual 
case in the foregoing table. 1. What seems to be the nearest whole number of degrees 

to express the rate of diminution? Do not take an average, the figures are not comparable. 
This decrease of temperature is due to the fact that as you ascend from the earth you go 
away from the immediate source of most of the heat of the air. If, however, air rises and 
cools by expansion against pressure, its decrease of temperature is 5.2° per thousand feet 
of rise. 2. That being the case, what would be the temperature which Geneva air 
would assume if lifted to Chamonix? 3. Under those circumstances would it weigh 
more or less per unit of volume than the Chamonix air? 4. What would happen to it? 
Try the same in several cases. 5. What do you find to be true? 6. From this 

would you conclude that cold air is always heavy, hot air always light. 

The United States Weather Bureau 
58. Every morning observations are taken of thermometers, wind vanes and other 
instruments at some ninety stations in various parts of the United States. The results, 
together with some contributed from neighboring countries, are combined by telegraph to 



29 

make a daily forecast of the weather. The total cost of the service of the Weather Bureau 
to the nation is near a million and a half dollars a year. What do the people get for their 
money? Not certain forewarning of every rain. That the Weather Bureau cannot give. 
What we do get from the Weather Bureau, however, is worth many times the appropria- 
tion every year. It is a service in three forms: (l)The saving of life and property in 
ships on the seas and lakes by warning the people of dangerous storms, (2)' the saving of 
life and property along great rivers by warning the people of dangerous floods, and (3) 
the saving of perishable foods, growing or in transit, by warning the people of severe 
frosts. Vessels in port, on the great lakes or oceans, are warned by the Weather Bureau 
of every serious storm that is liable to affect them. There are practically no failures in 
these warnings. The slighter changes in the weather cannot be predicted with certainty, 
but the great ones that endanger life, can be foretold with great accuracy, and none of them 
now find us unawares. Prudent shipmasters remain in port on such occasions. How real 
is the saving that comes from these warnings is shown by occasional failures of captains to 
heed them, as in the disastrous case of the Portland, at Boston, November 26, 1898.* 
Another storm that afforded many illustrations of the utility of the storm warnings was 
the great Gulf storm of September 1906. t Almost equally great is the saving accomp- 
lished by the river service, notably in the Ohio and Mississippi valleys where many people 
live. No dangerous rise in these rivers but is foretold by the Weather Bureau in time for 
dwellers on the lowlands to escape to the higher land and carry movable property beyond 
the reach of flood. Even the probable hour and height of flood at various points is pretty 
well announced beforehand. A recent illustration was the Ohio flood of February 19, 
1908. t So many perishable foodstuffs, largely fruit and vegetables, are now constantly in 
transit across the country, so many grow in regions like California and Florida, liable to 
be visited by destructive frosts, that forewarning of all cold waves makes possible great 
saving of property by protecting growing crops from frost and warming or affording 
other artificial protection to those in transit. Reference might be made to the frost of 
January 20, 1908, in Florida. § Shippers of such goods now rarely fail to inquire of the 
Weather Bureau about the temperature conditions to be expected during the time of an 
important shipment. There is certainly no department of the national government that 
brings a handsomer return on an investment of the people's money. 

EXERCISE 10.— Drawing Isotherms 

59. We shall best familiarize ourselves with the details of the daily weather map if 
we practice some parts at least of its construction. Too this end we will use data tele- 
graphed to Washington to construct a map of isotherms. 

Isotherms are lines drawn through places having the same temperature. They are 
commonly drawn at intervals of 10° though places having temperatures evenly divisible by 
ten, as 0°, 10°, 20 , 30°, etc. Usually the temperatures given are either higher or lower 
than the desired temperature. In such cases do not merely draw the isotherm between the 
two places, one of which has a higher and one a lower temperature than the temperature 
desired, but make an exact estimate each time. We have 27° and 35° for instance and 
wish to place the isotherm of 30° in that neighborhood. We should place a point ^ of 
the distance from the place having a temperature of 27° to the one having a temperature of 
35° and through that point draw the isotherm. 

*Monthly Weather Review, 1898, p. 493. tMonthly Weather Review, 1908, p. 19. 

tMonthly Weather Review, 1906, p. 416. ^Monthly Weather Review, 1908,. p. 2. 



30 



Makiug use of the above principle in drawing isothermal lines, draw the isotherms for 
one of the days, the data for which are given below: 



Kleva- 

tion in 

feet. 



Pressure 



Tempera- 
ture 



Kleva- 

tion in 

feet. 



Pressure 



Temprra- 
ture 



Father Point 

Chatham 

Halifax 

Quebec 

Montreal 

Albany 

Boston 

New York 

Parry Sound 

Buffalo 

Oswego ..., 

Binghamton 

Philadelphia 

Washington 

Norlolk 

Charleston 

Sault Ste, Marie,.. 

Alpena 

Saugeen , 

Detroit 

Toledo.. 

Erie 

Cleveland 

Cincinnati ..." 

Knoxville 

Jacksonville 

Tampa 

Key 'W, est 

White River 

Port Arthur 

Marquette 

Escanaba 

Green Bay 

Milwaukee ; 

Chicago ,.. 

Louisville 

Cairo 

Chattanooga 

Memphis 



100 

100 

227 

293 

60 

97 

125 

314 

600 

768 

335 

123 

117 

112 

57 

48 

624 

609 

656 

730 

674 

714 

762 

628 

10C4 

43 

36 

22 

1147 

608 

734 

612 

617 

671 

824 

525 

359 

762 

399 



30.40 
.40 
.38 
.42 
.42 
.43 
.44 
.43 
.30 
.39 
.42 
.42 
.42 
.41 
.41 

24 
.17 

23 
.32 
.30 
.28 
.36 
.32 
.25 
.24 
.18 
.15 
.14 
.08 

05 
.13 
.17 
.16 
.28 
.18 
.22 
.13 
.21 
.05 



30 03 



.00 
29.64 
.55 
.66 
.67 
.73 
.67 
.75 
70 



.77 
.83 
.87 
.96 
.86 
.79 
.73 
.86 
.90 
.80 
29.88 
30.01 



29.98 



30.01 
03 
.12 

30.02 



29.97 
29.97 
30 01 
30.05 
.01 
.05 



-7 
-13 
20 
-4 
-1 
7 
9 
13 
10 
12 
7 
8 
20 
20 
26 
40 
21 
17 
10 
20 
22 
15 
18 
28 
33 
46 
50 
63 
22 
17 
20 
20 
23 
28 
30 
31 
36 
37 
33 



43 



50 
50 
56 
62 
62 
66 
49 
59 
59 



68 
71 
73 
7f 
43 
50 
49 
60 
61 
61 
64 
64 



75 



78 
37 
36 
39 



56 
58 
65 
66 
70 
68 



Duluth 

St. Paul 

Lacrosse 

Davenport 

Kansas City ... 
Fort Smith.... 
New Orleans.. 

Galveston 

Minnedosa 

Winnepeg 

Moorhead 

Huron 

Omaha 

Dodge 

Abi'ene 

Qu'Appelle .... 

Bismarck 

Pierre 

Rapid City.... 
North Platte.. 

Denver 

Prince Albert.. 

Battleford 

Swift Current. 

Havre 

Miles City 

Lander 

El Paso 

Calgar> 

Medicine Hat. 

Helena 

Modena 

Kamloops 

Spokane 

Wiiinemucca.. 
Los Angeles... 
Portland, Ore. 
San Francisco 



702 

837 

720 

599 

963 

481 

54 

54 

1671 

757 

935 

1306 

1103 

2504 

1749 

2134 

1674 

1460 

3251 

2826 

5290 

1398 

1500 

2423 

2494 

2372 

5372 

3767 

2263 

2171 

4108 

5000 

1160 

1943 

4340 

330 

153 

153 



30.02 
29.96 
30.03 
30.04 
29.98 

29 86 
30.02 
29.87 

30 12 
.12 

30.12 

29 89 
29.85 
29.69 
29.77 

30 09 
30.12 
29.95 
30.01 
29 84 
29.95 
30.27 

.31 
.30 
.30 
.10 
.13 
.00 
.35 
.33 
22 
.31 
.31 
.40 
.36 
.23 
.20 
30.29 



.17 
.15 
.08 
06 
.13 
.06 
.03 
.01 
.43 
.43 
.32 
.34 
.20 
30 08 

29 98 
30.34 

.44 
.40 
.38 
24 

30 17 
30.27 

.24 

.27 

.25 

.36 

30.20 

29.88 

30.13 

.23 

30.18 

29.88 

29 98 
30.11 
29.99 

30 02 
30.00 
30.03 



2b 


40 


31 


48 


31 


53 


32 


60 


33 


63 


38 


71 


48 


75 


53 


76 


00 


41 


10 


41 


23 


44 


20 


48 


30 


56 


30 


64 


51 


73 


11 


40 


15 


43 


22 


48 


22 


48 


26 


55 


26 


56 


6 


41 


7 


43 


15 


43 


21 


44 


21 


45 


20 


50 


40 


72 


8 


48 


15 


46 


25 


47 


19 


49 


17 


60 


31 


50 


18 


51 


43 


57 


37 


60 


42 


58 



Weather Isothermals, Surface Isothermals, and Sea Level Isothermals 

60. When we wrote thermometer 
readings on the map and drew isotherms 
through places of the same temperature 
and between cooler and warmer places, 
we were preparing a map showing 
WEATHER. Most of the isotherms used 
in books are climatic and show average 
or usual conditions rather than actual 
ones. In such cases the numbers used 
are the averages of long series of obser- 
vations. If all the temperatures for the 
month of June for many years are 
averaged and represented by isothermal 
lines, the result is climatic and shows 




Fig. 11. Normal Surface Temperatures for June 



31 



the distribution of temperatures usual at that season. Such a map is the accompanying 

figure 11, showing normal surface temperatures for the month. It is supposed to show 

the temperatures to be expected at any place in the country at any time. It fails to do 

so, however, at present, because the number of points of observation is entirely too small. 

Some stations are high and, therefore, cooler than neighboring places, others in valleys are 

warmer than the country around. Isotherms drawn from such data cannot expect to 

represent the country correctly. Thus two valley stations in the mountains might each 

have a temperature of 30 degrees. But the isotherm drawn from one to the other might 

very likely pass across a mountain range, several thousand feet above. The temperature 

up there may be near zero, yet the map reports it as 30 degrees. Any such map has 

this defect unless the observation stations are numerous enough to represent the actual 

topography, which is never the case. The difl&culty is met by " Reduction to Sea Level." 

The air is known to be cooler and cooler as one ascends above the level of the sea. From 

kite and balloon studies and others along the slopes of the mountains, it is seen that the 

temperatures of high places are lower than they would be if the ground were lower. A 

series of corrections has been prepared by which temperatures at all heights are reduced to 

the level of the sea. The United States Weather Bureau adopts the following values : — 

December to February 1°.5 per 1000 ft. 

March to May and September to November 2°.0 per 1000 ft. 

June to August 2°. 5 per 1000 ft. 

Thus a place 5000 feet above sea level has a normal surface temperature for June of 
62.5°. The reduction to sea level for that time and height is 5 times 2.5° or 12.5°. The 
corresponding sea level temperature is 75°. If all the values are so reduced to sea level, 
and a system of isotherms drawn with the resulting numbers we shall obtain the distribu- 
tion of temperatures 
about as they would 
be if the whole surface 
of the country could 
be smoothed down to 
the level of the sea. 
Fig. 12 is such a map 
of sea level isotherms 
for June. Though it 
does not correspond 
to any actual condi- 
tions, it does enable 
us to learn the normal 
surface temperature at 
any point and any 
elevation. Thus the 
sea level June normal 
for Toledo is 70°, the 
elevation 6 74 feet. 
Subtracting ^ of 2.5° 
11. 




Fig. 12. Sea level normals for June 
or 1.6°, we have a surface normal of 68.4°, about as shown by Fig 

EXERCISE 11.— Spells of Weather 
61. Construct temperature curves for January, for both Ypsilanti and Havana, using 
the mean temperatures of the days as given in the right-hand columns of tables 48 and 49, 



32 

calling each square of quadrille paper one degree vertically and horizontally one day. 
Both curves may be placed on one diagram. 1. Does any diurnal sun effect show in 
this curve? 2. Does either curve show that the air got steadily warmer or colder 
through the month? 3. Which curve shows the more distinct spells of weather? 4. 
How many warm spells at Ypsilanti? 5. How many cold? 6. How many days did 
that make a spell last on an average? These spells are the special characteristic of our 
weather except, usually, in May, June, July and August. Now construct diurnal curves 
for both places with the mean hourly temperatures from the bottom of the tables. Put 
them on the same diagram, using the same temperature scale but calling one square hori- 
zontally one hour. This enables us to compare the diurnal temperature ranges with what 
we might call the spell ranges, the differences between the cold spells and the warm ones 
that follow or precede. .7. At which place is the spell range greater than the diurnal? 
8. How many times as great? This too is characteristic, a feature of the climates of 
these places. At the one place temperature changes are mostly from daylight warmth to 
nightly cooling, at the other this signifies much less than change from warm spell to cold 
and back. At one of the places days may be even colder than nights, as on January 7th 
and 11th. 

Irregularity of Temperature Distribution in Longitude 

62. From the isothermal map it appears that places, on the same parallel of latitude 
have differing temperatures. This is not only due to different elevations above the sea, 
but also because the sun's rays fall on surfaces so different even where the rays have the 
same inclination. Land and water do not heat up equally under the sun, nor do bare and 
grass covered lands. The red and yellow desert of North Africa, the blue Atlantic, and the 
plant-covered lands bordering the Gulf, do not undergo equal heating, so it is not strange 
that the air above them has varying temperatures. A continent or large island, like 
Australia, Madagascar, New Zealand, or Great Britain is always warmer than the neigh- 
boring sea in summer and also cooler in winter ; for the laad not only heats up more under 
the sun's rays, but also cools off faster in winter. 

Seasonally and with the spells of weather that succeed each other in our latitudes very 
great differences in temperature result from the importation of southern and northern air 
on the wind. Spring is due with us, for instance, when the sun reaches a certain eleva- 
tion in the sky; it is apt to come with a week of south wind. 

Pressure 

63. It has been pointed out that we live at the bottom of the ocean of air just as the 
inhabitants of the sea bottom pass their lives at the bottom of the ocean of water. But the 
gaseous nature of our atmospheric ocean gives it great peculiarities. A shell fish in deep 
water has always the same amount of water above him, and about him it is always still. 
There are tiny changes in the quantity of water as waves pass above, and there are slow 
movements of sidewise drift and currents. Entirely insignificant, however, both of these 
in comparison with what occurs in the air. We have very great differences in the amount 
of air above us and it moves about on the earth's surface with the high velocity of the 
storm winds. Some knowledge of the varying amount of air above is necessary to under- 
stand the winds. It is not possible to feel it directly; its manifestation is in that some- 
what vague thing called air pressure, and the instrument that shows it, the barometer. It 
is so grounded, however, on changes of temperature that we may form an idea of it very 
readily by noting temperature changes. Paragraph 35 will help the student see what a 
barometer is and how air pressure is only a vague name for the quantity of air over the 
spot being studied, 



We shall now regard the rising of the barometer as indicating that more air is coming 
to the region, its falling as signifying less air present, z. e. some air is going away. 

Balancing Columns, Water and Mercury 

64. Materials: 2 glass jars, 18 inches high, and 3 and 1/^ inches wide respectively. 
1 glass tube, 36 inches long, /4^-inch wide. 1 pound of mercury. 

Put some mercury in the bottom of the smaller jar, stand the glass tube in the mer- 
cury, and pour water upon the mercury in the jar until the water is 13 inches deep. Note 
what happens within the glass tube. Make a measurement of height above mercury in jar. 
If the water is now withdrawn with a siphon, notice what happens within the tube as the 
water level falls in the jar. In siphoning, the water should be run into an empty jar, so 
that if any mercury comes over it may not be lost. If the water in the service pipe con- 
tains lime or other salts, distilled water should be used. 

Repeat the experiment in the larger jar. When you have a column of water 13 inches 
deep over the mercury in this jar, how does it compare in bulk and weight with the water 
in the first experiment? Suppose we had a jar a foot wide, and put water in it 13 inches 
deep over mercury in which a tube had been previously placed, what would happen within 
the tube? 

Suppose a bowl of mercury with a tube standing in it were placed in a pond or tank, 
so that the mercury was just 13 inches under the water surface, while the tube projected 
above the water surface, what would happen? 

What one quantitative condition must always be fulfilled in these experiments to get a 
column of mercury to balance a 13 -inch column of water? To balance any column of 
water? 

In all these cases both fluids have been visible, but once we know the principle, the 
water might be concealed, and we could still judge of its height very accurately by the 
height of the mercury in the tube. 

We might in the same way balance a column of gas against the mercury. Thus the 
heavy violet vapors of iodine weigh 1/1207 as much as mercury? How long a tube filled with 
iodine vapor would balance one inch of mercury? How many inches? How many feet? 
In the calculation we might disregard the compression of the vapor in the bottom of the 
column by the weight of the vapor above. That would require a long tube, indeed, but it 
would be conceivable. Although it would be balancing gas against liquid, both would 
still be visible on account of the violet color of the gas. But as long as the mercury is 
visible, the same balance might be made with a colorless gas like air. Air under standard 
conditions weighs Viooit as much as mercury. How many inches, feet and miles of air 
in a column would balance an inch of mercury? 

65. A barometer is really a tube in which a column of mercury balances the atmos- 
phere of air. By the height of the mercury column we judge the height the air column 
would have if it were of uniform density and composition throughout. The mercury in 
the barometer at sea -level, stands about 30 inches high. How high a column of homoge- 
neous air, equally dense from top to dottom, would that represent in miles? 

We have thought of a bowl of mercury in which a tube is placed and the whole 
lowered into a pond. As long as the tube projects above water, its walls keep the mercury 
within from experiencing the pressure or weight of the column of water that rests on the 
mercury in the bowl without. As for the atmosphere in these experiments, it presses on 
the mercury inside the tube and on the water without alike, so it is just the same as if it 
exerted no pressure at all. 



34 

Now our thought of the atmosphere is of a widespread layer of air resting upon the 
earth, thin or rare above where the high mountains reach up into it, thicker or denser 
below where the weight of the upper layers that rest upon it press it together. There is 
probably air a hundred miles above the surface of the earth, yet remembering that the 
earth is 8000 miles through, while vastly the greater part of the whole atmosphere is com- 
pressed into the lower ten miles, we see that it is a relatively thin film, fairly comparable 
to the skin of an apple. Let us now try to imagine a bowl of mercury with its tube set 
into this ocean of air just as we thought of another set into a pond. The tube must always 
be thought of as long enough to reach up through the whole thickness of the atmosphere. 
Thus there will be no air within the tube, it being kept out by by the glass walls. The 
mercury rises within the tube to balance the weight of air without on the surface of the 
mercury in the bowl. The hundred -mile -long tube would not be needed. If its walls 
could be fused together a few inches above the top of the mercury in the tube so as to keep 
the air out, the balancing would go on just the same. If more air came to that neighbor- 
hood, as in the crest of a wave, the column of mercury within the tube must rise to balance 
it. That is essentially what a barometer is, and how it works. 

66. That " the air presses " is believed to be an easier conception for beginners than 
the " pressure of the air." As a form of words both may mean the same thing, but only 
one reality, the air, is involved, and the first statement may be regarded as the direct state- 
ment of fact. The pressure, on the other hand, has no real existence except as a word. 
It is not a thing at all. Suppose the result of the action be a broken window. It is the 
air that breaks it and not the pressure. This is just as true as if we were talking of a ball 
flung at the window. The ball really breaks the glass, though we may use a variety of 
other phrases about it, each of which may have some value of its own ; as, the force of 
the ball breaks the window, the momentum, etc., the glass was broken by the impact of the 
ball, a boy broke the glass with a wild ball, the blow of the ball upon the window broke it. 
Yet upon examination it appears every time to be the ball that breaks the glass. All 
abstract nouns have the same indirect relation to reality. Thus in the sentence " This 
man's influence on the community is powerful," the influence is the subject of the verb, 
but the man is the real agent. This appears in the direct statement, " The man influences 
the community strongly." " The wife's energy supplemented the ability of the husband." 
This becomes in the direct form, "The energetic wife helped the able husband." It is 
not pretended that the direct form is universally preferable. In the last example the first 
or indirect statement is much better. But in cases where quantities enter that are to be 
measured and thought of as acting, there is a great gain for elementary presentation in the 
direct statement and the avoidance of the abstract noun. It is air that affects the barome- 
ter, and not pressure of the air. If more pressure does not imply more air, it means 
nothing at all. Of course there is no reason why anyone who has once become familiar 
with the instrument should avoid the convenient word. But, though entirely justified and 
in the very best use, it is often a cause of early misunderstanding. 

Barometer Corrections 

67. Unlike the thermometer, the barometer readings need correction before they are 

transferred to the weather map. The corrections are two, for temperature and elevation. 

Since mercury expands with heat, the amount of mercury needed at any moment to balance 

the atmospheric column will measure more or less inches according as the instrument is in 

a cold or warm room. To have a means of comparing the readings of different instru- 

ts, it is necessary to allow for the temperature by calculating what the length of the 
men 



35 

column of mercury would have been had the temperature been that of freezing water. 
This is called the reduction to freezing point and must be applied to all readings of good 
barometers. 

The reason for the second correction, the reduction to sea level is that we desire to 
know the distribution of atmospheric pressures at some uniform level. That the pressure 
varies at different levels we know. To understand the winds it is necessary to find out 
whether it is constant at any one level. So the readings are always reduced to sea level. 

Read the thermometer and barometer outside the window and those within. Where 
is it colder? How much? Where is the barometer ' 'higher? " How much? Divide the 
difference in barometer readings by the number of degrees difference in temperature to 
ascertain how much the outer barometer seems to have fallen per degree of greater cold 
outside. The published tables of corrections for temperature allow for the expansion of 
the mercury, the glass tube, and the brass scale and do not apply to a barometer with 
wooden scale such as is used in these experiments. The wood is more affected by 
moisture than heat, but changes with absorbed moisture are too irregular to be calculated. 

The amount added for reduction to sea level is rudely indicated by the following table : 



Outside Temperature 


0" 


30° 


60° 


90° 


Elevation 


In. 


In. 


In. 


In. 


1000 feet 


1 21 


1.13 


1.06 


1.02 


2000 • ' 


2.34 


2 21 


2 08 


1.97 


3C00 ' ' 


3.45 


3 25 


3 07 


2.91 


4000 ■' 


4.51 


4.25 


4.02 


3.83 


5000 ' ' 


5.52 


5 22 


4.86 


4.69 



Reduce your outside observation to sea level. 

EXERCISE 12— Drawing Isobars 

68. Isobars are lines drawn through places having the same air pressure. They are 
commonly drawn on weather maps for intervals of one-tenth of an inch through places 
having pressures ending in even tenths as 30.1, 30.2, 30.3, 30.4, etc. In many places 
where pressures are given they are higher or lower than the desired pressure. In such 
cases do not merely draw the isobar between the two places, one of which has a higher and 
one a lower pressure than the pressure desired, but make an exact estimate each time. 
We have, for example, two places having pressures of 30.10 and 30.30 and wish to draw 
the isobar of 30.20 in that neighborhood. We should locate a point just half way between 
the two places and draw our isobar through that point because 30.2 must necessarily lie 
just half way between 30.1 and 30.3. The method is the same one used in drawing iso- 
therms. 

Making use of this principle as shown in the class exercise, chart the isobars for one 
of the dates for which data are furnished in the table in section 59. 

Relation of Air Temperatures and Pressures 

69. The system of isobars drawn with the readings for date A shows a grouping of 
low barometers in the central valley, west of the Mississippi with higher barometer read- 
ings grouped over the Rockies and again over the Allegheny mountains; for date B high 
barometers on the 100th meridian and low in the St. Lawrence valley. Remembering that 
the readings have been reduced to sea level, what thought about the depth of the air over 



36 

various parts of the country would explain such distributions of pressure on the supposi- 
tion that the temperature is the same everywhere? Does that suggest a level upper surface 
of the atmosphere like that of the ocean? Of course our supposition is improbable. The 
temperatures are not the same everywhere. The isothermals show differences even on the 
same parallel of latitude. You have learned from the daily weather map, that there is 
definite association of temperatures with the areas of high and low barometer. You are, 
therefore, in a position to judge the sort of error involved in our assumption of uniform 
temperatures all over the country on dates A and B. What are the real conditions of tem- 
perature in the country that morning? As warm air expands and occupies more space, 
while cold air contracts and occupies less, we must modify our previous thought about the 
depth of air in various places. What shall we now believe about the air surface? 

70. The relation between pressure and temperature is a causal one. The pressure 
varies because the heat varies. Suppose the air over the continent of Australia to be 
warmer than the air around. Being warm the air tends to expand and mound up there 
overhead. 1. Would this make the pressure there less? 2. Would it make the air 
there weigh less? 3. Would the barometers go up or down because of this tendency 
to expand? 4. Why not? 5. Is a bar of iron lighter or heavier when hot? 
6. Why should a mass of air be? 7. Is it true that warm air is light? 8. If some air 
in a bag weighs a pound, will it weigh less when we warm it? The only sense in which 
warming makes it lighter is that it expands and occupies an amount of space that would at 
the lower temperature be occupied by a greater amount and weight of air. 9. What 
will happen instead? 10. If some air goes away above how will that affect the 
barometers below over the sea? 11. How in Australia? 12. Under such circum- 
stances the winds will blow in towards Australia from all around. This actually happens 
every summer. 13. Why? 14. Would you say such winds are caused by tem- 
perature or differences of temperature? 15. Which is the more immediate cause, dif- 
ference of temperature or difference of pressure? 16. What causes the difference 
of pressure? The sun's heat causes a change in the condition of the air. 17. What 
is this change? Motion is involved in this change, but it is motion within the mass and 
not motion of the mass. The familiar statement that hot air rises is convenient some- 
times, like the statement that the sun rises, but neither is exact. The lower air is always 
much warmer than the air high above the earth, but it is usually quite content to stay 
below without any tendency to rise, being so compressed by the weight of the air above 
that is not so light, quart for quart as it is. Expansion, with motion within the mass is 
the only direct result of heat. But this expansion gives an opportunity to another force 
to cause motion of the mass. 18. What is this force? 19. Is the first tendency to 
motion of the mass active above or below? It is at this moment that change of pressure 
appears. The pressure of the air is merely a manifestation of its weight and cannot change 
unless the quantity of air changes. If air goes away there will be less air, less weight and 
less pressure. And wherever more air goes there will be more air, more weight and more 
pressure. The depth of the atmosphere to sea level is to be thought of as fairly con- 
stant since an excess of depth anywhere at once begins to find a remedy by the action of 
gravity. 

71. Heat causes a tendency to expand; expansion gives gravity a chance to move off 
air above, this causes unequal pressures within and without the warm area in the air below, 
unequal pressure below sets the lower air moving or causes winds. Do the winds then 
generally move towards places that are cooler or warmer than places around? It is 
familiar that the sun is always high in the sky near the equator, causing greater heating 



37 

there than nearer the poles. Nearer the poles are alternate seasons of high sun or summer, 
and low sun or winter, when the rays more nearly graze the earth's surface and warms it 
much less. Thus the strip of highest temperature and lowest pressure migrates across the 
equator with the sun twice each year. We shall presently find winds and rainfall migrating 
similarly. The mercurial barometer should now be read daily and the result recorded in 
the note book. Saturday and Sunday readings may be taken from the the barograph sheet 
posted every Monday. The barograph should also be glanced at each day to see whether 
the barometer is now rising or falling, and this fact be recorded. 

EXERCISE 13.— Inferring Isotherms to Isobars 

72. By a study of our collection of mounted weather maps or the series printed on 
pp. 41-50 determine which is warmer, the front or the rear of the cyclone. Notice how 
this is expressed by the isothermal lines. To discover this the student had best confine 
his attention to low pressure areas that are strongly developed and which are shown com- 
pletely, i. e. are not partly over the ocean. From these same maps determine which have 
the lower temperatures associated with them — areas of high or low pressure. The tem- 
peratures you are here concerned with, are those along the same parallel of latitude. You 
are to note the temperature along the same east and west line through a cyclone, or from 




Fig. 13. Pressures for March 3, 1904. Isotherms to be added by the student with the help of 
temperatures marked at the eastern coast. 



cyclone to anticyclone. You will be helped by considering whether it becomes colder or 
warmer at a place where isotherms that pass to the south are bent northward toward it. 
Note the effect that areas of high and low pressure have upon the direction of the isotherms. 
After you have succeeded in determining to your satisfaction the temperature relations 



38 



existing in the cyclone and between the cyclone and anticyclone, express it in isotherms 
on one of the engraved maps of isobars accompanying the exercise Fig. 13 and 14. Draw 




Fig. 14. Pressure system for January 19, 1904. Isotherms to be put in by the student with 
the help of temperatures marked at the coast. 

your isotherms at intervals of 10°, using as your starting points the temperature given on 
the map and estimating for intermediate temperatures. Draw your isotherms just as 
though the only factor causing them to deviate from a straight east and west line was the 
area of high and low pressure. 

Winds 

73. The wind is the lower air moving. The motion is from a region of high pressure 
to one of low pressure, and these differences of pressure almost always have their cause in 
differences of temperature. Among the simplest cases are the continental winds of 
Australia, referred to in paragraph 70, and shown in the diagrams (Figs. 15 and 16). 



-. 1L«-^ ^ 


V5^'^\i 


^^^^!I^s^j^-^ j^ / 


hi 


ult 


- p 


VTl^ 


-m 




Fig. 15. January. Fig. 16. July. 

EXERCISE 14.— Cyclonic Winds 
74. By an inspection of the weather maps(pp. 41-50) for Jan 20, 21, 22, 23 and 24, 
1902, what would you decide to be the general movement of the air around areas of low 
pressure — toward or away from the center? 



39 

2. On the map of Jan. 21. 1902, how do the winds seem to be blowing about the low 
pressure area centered over eastern Tennessee? 3. Are they blowing straight toward 
the center? 4. If not, to which side of center, right or left? Look straight north of 
the area on Lake Erie. 5. If the winds there blew straight at the area they would be 
north winds. 6. Are they? If they go west of south they turn to the right i. e. to 
THEIR right of straight ahead. 7. Do winds at stations straight to west of Tennessee, 

go toward southeast (right) or north east (left)? 8. As you look at the other maps 
again, does the same thing seem on the average to be true? 

State in general terms the movement of the air around the cyclone. Illustrate by a 
diagram, using six arrows to show the direction of the wind, and show to the instructor. 
Make the shaft of each arrow straight and one -half inch long. 




50 60 70 80 90 100 110 

Fig. 29. Winter monsoon, January, February 



120 



50 60 70 80 90 100 110 120 




Fig. 30. Summer monsoon, July, August 



40 

75 How will the land and sea pressures near A.ustralia compare in December? Such 
seasonal alternations of the winds from the sea and land are called monsoons. North 
America has less pronounced but perceptible monsoons. (Fig. 27 and 28). They are 
most strongly developed in the northern Indian Ocean. (Fig. 29.) 2. In what season 




Fig. 27. 'Average winds of the United States, December 




Fig. 28. Average winds of the United States July 

will southern Asia be warmest? 3. When will it have the lowest pressure? 4. 
Why does the southwest monsoon blow there in summer? 5. Why the northeast mon- 
soon in winter? 



41 




42 




43 




44 




45 




46 




47 




48 




4§ 




5o 













— — 




o o 

ID ^ 








CO 






00 


o> 








o 
<s> 

o 

r^ 

o 

00 

o 
<J> 

o 
o 

o 
o 

CM 

o 

CO 


^ 


A M 

7i 



K 

. . . r . . . ;s \ 





00 

7 


] i 




\\ 




^^ 




i-A 


■Y:':-:-//! 


z ^ 

LO 


}.s:^y.:'.v: :::::.■ 


: : .V-.- ; : .• .y-; 




■•«■•■" 






/?: : : ,i/: : : : : . ; 


yf • 


\\. ..<.. :..,.. ;...:,. 
. ' >, 


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/ ■ y 


Jr. . : •.._ 


v^ 


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"^"^T^b^ 




s 

10 ^^ 






S 





51 

Land and Sea Breezes 

76. When such an alternation of winds is diurnal instead of seasonal, they are called 
land and sea breezes. Like all winds these are named from their point of origin. They 
are observed on most sea shores and on many lakes, being distinct in summer on Lakes 
Huron and Michigan, on days of feeble general circulation of the air. In winter the land 
is usually colder than the lake, even by day, so the lake breeze is absent. 

Lake or sea breezes that blow by day to the heated land are always stronger than the 
land breeze of the night, mostly because the rougher land surface offers more resistance to 
the passing of the air than the water does. It is always the case that the wind blows faster 
on the water than on land. For the same reason, kites, balloons and clouds show the 
movements of the upper air to be much more rapid than the winds below. Mountain 
winds confirm us in this view of the effect of friction in retarding the wind at the earth's 
surface. 

Average wind velocity in miles per hour at various shore and inland stations: — 



Block Island 


17.2 


Key West 


10.5 


Boston 


11.8 


Salt Lake City 


6.0 


Chicago 


17.0 


San Francisco 


10.6 


Cincinnati 


7.7 


Wood's Hole 


15.8 


Galveston 


10.9 


Denver 


8.0 


Hatteras 


13.9 


Pikes Peak 


18.0 (36.0 in winter) 


Kansas City 


8.6 


Mt. Washington 


34.0 



EXERCISE 15— Anticyclonic Winds 

77. Examine the weather maps for January 20, 21, 22, 23 and 24, 1902, and deter- 
mine whether the air around the areas of high pressure seems to be moving outward or 
toward the center of the area. 

1. On the map for January 23, do you detect anything besides the outward movement 
of the air? 2. Do the winds blow straight out, to the right of straight out, or to the 
left of straight out? 3. Do you discover any verification of your conclusion on the 
maps for other days? 

State in general terms the movement of the air in the anticyclone. Illustrate by a 
diagram as you did for air movement in the cyclone. 

The Winds of Observation 

78. "We should gather material for the study of the winds by noting the direction and 
force of the wind each morning with the principal changes during the day. We may use 
the data gathered from a wider area on the daily weather map, and we may note the effect 
of the prevalent wind on the trees. This is often well shown on fruit trees, which yield 
the more readily as the ground is kept soft by cultivation, unless, indeed, the farmer has 
been prudent enough to plant his trees leaning against the wind, as is sometimes done. In 
what direction does this make the tree lean with us? Select isolated trees in the country, 
to which the wind has free access, and note the unequal development of the branches. 
The best time to observe this effect is in the leafless season, when the growth of the twigs 
is seen to be much influenced. Most affected, perhaps, are the poplars, and after them 
the willow, maple, elm, buttonwood, hickory, oak and black walnut, in order. The Cot- 
tonwood appears to yield very little to the influence. Find examples of this influence of 
prevailing winds. If the wind observations have been kept since the beginning of the 
course, it now appears clearly that the west ones are the more frequent. 1. What per- 
centage of all have you in that direction? 2. Is the wind effect on the trees in the 
same direction? The winds of observation for us are in the northern belt of westerly 
winds. They extend around the world between 30 and 60 degrees of north latitude. 



5^ 

There is a similar belt in the southern hemisphere and in these two regions live the mosi 
progressive and energetic races of the world. But we do not need to keep weather obser- 
vations to know that there are many other winds than westerlies here. In the laboratory 
exercise on the winds about areas of low barometer we found them blowing in every direc- 
tion, it is true, but with two common rules of conduct, so to say. 3. What were these? 

79. The diagram of planetary winds, Fig 31, shows the average winds as they 
Urould blow on an eairth without land. They are not real winds of the weather. None of 




Fig. 31. The winds as they would be on an ocean-covered globe 

our east winds show for instance, since they are fewer than the west winds and disappear 
in the average. Also all land winds are weaker than sea winds because of the friction of 
the surface of the land. So both trades and westerlies are much checked on lands. 




Fig. 32. World Isobars 




53 

EXERCISE 16— Wind Effect on Trees • 

80. Our winds are prevailingly from the same 
general direction. This is shown plainly by many 
trees. 

Go from the city westward in open country. 
Examine the trees from the southward or northward. When you think you perceive a 
wind effect, go to a point east or west of the tree. Is it now symmetrical? Sketch the 
the tree from two directions at right angles. Observe and describe the wind effect on it. 

EXERCISE 17.— Monsoon Temperatures 

81. Construct curves of daily temperature at Calcutta and Nagpur, India, from the 
following data using one square of the quadrille paper vertically for one degree and two 
squares horizontally for a month. 

Both places should be looked up in the atlas. Calcutta 
is in latitude 22i N., 88| E; Nagpur in 21 N., 79 E. 
Notice the date of maximum temperature on these two 
curves. 1. Is it usual? See paragraph 45, 2. 

Which monsoon is blowing in India in summer? It blows 
much more strongly than the winter monsoon, and comes 
on very suddenly. 3. Does anything on the curve 
indicate the change in the monsoon? 4. What is the 
date of the change, apparently? 5. Why does the 

maximum temperature come early at these places? 



January 64 

February 70 

March 80 

April 85 

May 85 

June 84 

July 83 

August 82 

September 82 

October 80 

November 73 

December....... 65 



Calcutta Nagpur 

68 
74 



83 
88 
94 
86 
80 
80 
80 
79 
72 
67 



82. The fact of rotational deflection may be simply stated thus: 

For a person in the northern hemisphere the earth turns from right to left. This 
causes all straight lines on it to turn to the left. A body, or mass of air that starts off 
along a line holds its direction and therefore seems to turn to the right. When we go into 
the southern hemisphere our point of view has changed, it is as if we looked at a picture 
from the back. The earth and lines on it turn to the right and whatever moves off straight 
starting on a line, seems presently to turn off to the left from that line. The deflection is 
greatest at the poles and nothing at the equator. Why are such winds about a low bar- 
ometer and their attendant circumstances in the air called a cyclone? Why are the winds 
and other conditions about an area of high barometer said to make up an anticyclone. 
Perhaps the most interesting thing about an anticyclone is that its winds are really gov- 
erned by the same two rules of conduct as the cyclone. Both are illustrated on the 
diagrams of Australia and its seasonal winds. 1. When is the Australian wind system 
like a cyclone? 2. When is it like an anticyclone? 3. Is there not a difference each 
time? 4. Did you learn from *Foucault's pendulum why the trades have more 
southing than the westerlies have northing? Of course in the southern hemisphere the 
sun moves from right to left since the people there live, as it were, on the under side of 
the equator and see all our directions reversed, just as a man would who read diagrams 
from the back of the paper. 

EXERCISE 18.— Inferring Winds to Isobars 

83. You have now determined the actual direction of the winds in the cyclone and 
anticyclone. 



*Foucault's Pendulum; Young's Astronomy, p. 110; Report Chief Signal Offloe, 1885, pt. 2, p. 181; Journal of School 
Geography, 1899, p. 298. 



S4 



On the isobaricmap which you constructed (Ex. 11), indicate by arrows the wind 
directions you would expect. Make each arrow half an inch in length and draw one for 
each 5° mesh of the map. 

Water Vapor, Clouds and Rain 

84. Water vapor is always present in the air. Even in the desert enormous quanti- 
ties of water are always present in this form. Water vapor is transparent and invisible. 
The bluest sky, the clearest air contains it. Clouds are made of little particles of water, 
not of water vapor. Mist is cloud seen from the inside. Cloud is mist seen from the out- 
side. The steam inside the tea kettle is invisible as would be noted were the kettle made 
of glass. Close to the spout nothing is seen to issue. Only a little way off appears the mist 
of water particles called steam. It really consists of water drops condensed from the steam 
by the cold air. Probably most of the water vapor in the air comes from the trade wind 
belts of ocean on either side of the equator. This map of the world, Fig. 33, shows the 
distribution of the salter parts of the ocean surface. 1. What has the great saltness of 

these parts of the ocean to do with the supply of water vapor in the air? 2. Are the trades 




Fig. 33. Saltness of ocean water. The saltest water is lined and the least salt is blank. 
growing warmer or colder as they advance? 3. Why? 4. Are they gaining in 
power to take up water? 5. Is the sky often cloudy in the trade winds? The per- 
centage of cloudiness in Fig. 34 will enable you to answer the question. 




Fig. 34. Lined areas have cloudy sky more than half the time. 



s^ 



§5. Vapor is formed from water at all temperatures. The water particles are believed 
to be in a state of rapid motion. Our thought of evaporation is that occasionally one of 
these particles near the surface plunges out into the air. This, as has been said, occurs at 
all temperatures, but naturally more at higher temperatures, when the particles are moving 
faster. When this process has gone on long enough to cause a great number of particles 
to exist in the vapor condition, it is not difficult to believe that occasionally one of these 
particles plunges back into the water. This should happen oftener as the space above the 
water becomes fuller of vapor. But presently there must come a moment when as many 
plunge in in a given time as emerge. At this moment the greatest possible amount of 
vapor exists in the space and it is said to be saturated. If more heat be now applied the 
emergence of particles becomes more active and more vapor can be contained in the given 
space. If it be cooled, emergence is checked and the quantity of water vapor that can be 
contained in the space is diminished. In usual phrase warm air has a greater capacity for 
water vapor than cold air, though the air has nothing to do with it; the same evaporation 
occurs into an empty space as into air and faster, perhaps because the air acts as a hin- 
drance to the movement of the particles. 

86. Experiment has shown that air containing 4 grains of water vapor to the cubic 
foot is saturated at 50°. That is at that temperature 4 grains and no more of water could 
be evaporated into it. If cooled below 50° some of the vapor will take the form of dew or 
cloud. Experiments further show that a fall in temperature to 30° would condense about 
half of the water vapor, while a rise to 70° would enable it to take up another 4 grains to 
the cubic foot if it could get at it. If it got no more water it would be said to have become 
drier in view of its increased capacity for moisture. For ordinary thought air is dry when 
it will dry other things. In this sense it is no part of drying air to take water away from 
it; on the contrary we might add two grains of water to the cubic foot while we raised it 
to 70°, and as it would still have a capacity for two grains of water it would be drier than 
it was at 50°. The effective moisture of the air is thus seen to be as much dependent on 
temperature as on water content. A better name for this sort of moisture is relative 
humidity. It is said to be 100 percent, when the air is saturated, as is air at 50° with 
four grains of water vapor to the cubic foot, but the same air heated to 70° without gain or 
loss of water would have a relative humidity of 50 per cent, containing only four out of a 
possible eight grains. 

87. To illustrate actual values of relative humidity, the following table is inserted of 
average monthly temperatures and humidities observed at Detroit in 1898, at 8 a. m., 
Eastern time: 



1898 



January ... 
February ., 

March 

April 

May 

June 

July 

August 

September 

October 

November 
December. 



Tempera- 
ture 



26.2 
24.1 
55.3 
40.8 
59.4 
66.1 
69.7 
67.8 
61.7 
49.1 
34.8 
25.4 



Grains Vapor to 
1 Cubic Foot of Air 



Possibly Actually 



1.67 
1.53 
2.42 

2 95 
5.64 
7.11 
7 91 
7.48 
6.12 

3 97 
2.. '8 
1.62 



1.44 
1 41 
194 
2.01 
3.61 
5.19 
6.17 
6 13 
4.83 
3.30 
1.95 
1 38 



Relative 
Humidity 



86 
92 
80 
68 
64 
73 
78 
82 
79 
83 
82 
85 



Pints Water 
Room 21 



3.9 

3.8 

5.3 

5 5 

9.2 

14.2 

16.9 

16.7 

13 2 

9.1 

5.3 

3.8 



56 



At the average temperature observed in January, 26.2°, 1.67 grains of water vapor 
suffice to saturate a cubic foot of air, but as there were present only 1.44 grains the relative 
humidity is said to be i--H'i.67 or 86 per cent. If our room measures 42 by 34 by 14 feet, 
multiplying the cubic feet in it by the grains of water to the cubic foot actually present in 
any month we shall get the number of grains of water present. Divide this by 7300, the 
number of grains in a pint, and thus verify one or two of the numbers in the last column. 
It seems surprising to find so large a quantity of water contained in the air. And the table 
shows that it is precisely in the summer months, when the sky is clear three-fourths of the 
time that the air contains most moisture, fully four times as much as in January when the 
sky is clear only a third of the time. Yet the summer air is drier, or better, the relative 
humidity is less, as the table shows. 1. How much vapor to the cubic foot can the 

January air still take up? 2. How much the August air? Strange as it seems the clear 
skies of August contain much more water vapor than the cloudy skies of February. The 
desert of Sahara has about as much water vapor in its air in summer as moist Eng- 
land, yet the desert temperature is so high that the air is dry, i. e. the relative humidity is 
not more than forty or fifty per cent. 3. What relative humidity is usual here? (See 
Climatology of the United States, Michigan.) 

" Thus the air even above the dry ground of the desert contains a considerable 
amount of water vapor, brought from the neighboring seas and coast regions by air cur- 
rents and by the diffu.sive power of the water vapor itself. The 
rainless character of the desert is caused, not by a lack of water 
vapor in the air, but by the absence of conditions leading to its 
condensation." 

88. The accompanying table contains the possible water 
contents at the given temperatures. 1. What was the water 

content in grains to the cubic foot of the air in the room at the 
time of the experiment? 2. How many pints of water? 

Construct a curve from this table, using one square of 
quadrille paper, vertically, for 2°, and horizontally for \ a grain 
of water vapor. 
EXERCISE 19 — Measuring Moisture in the Air 
Materials : A thermometer, glass of water and thin cotton cloth 1x4 inches. 

89. Take the temperature of the air in the room and the water, which should have 
the same temperature, and will if it has stood in the room long enough. Dry the ther- 
mometer and again take the temperature of the air. Place a little water on the thermome- 
ter bulb and note what happens. Can you explain? The warmth of the mercury is being 
used to do work. What work? Now wrap the bulb with the cloth which is twisted into 
a rude wick and dipped into the water in the tumbler. The temperature falls and in five 
or ten minutes will reach its lowest point. Note the temperature reached and by the fol- 
lowing diagram ascertain the relative humidity. 

Dry 73°, wet 71°, difference 2°, relative humidity 90 per cent. 

90. Human interest in the water vapor in the air is in its relative humidity which 
affects our comfort, and its precipitation, which conditions life. 1. What are the con- 
ditions that lead to the condensation of water vapor? The fall of temperature that will be 
thought of as the cause, is due to some upward movement of the air and the expansion 
that must result. Such ascents occur in the equatorial regions, in cyclones and at moun- 





Possible 


Tempera- 


No. of Grains of 


ture. 


Water Vapor 




per cu. ft. 


0° 


0.54 


10° 


0.84 


20° 


1 30 


30° 


1.97 


40° 


2.86 


50" 


4 09 


60° 


5.76 


70° 


7.99 


80° 


10 95 


90° 


14.81 


100° 


19.79 



57 




58 

tain slopes. The last case has already been referred to. 2. In the first two what lifts 
the air? 3. Are there any movements of the air round about that cause the central air 
to rise? 

It is now seen that there are several belts about the earth with rain conditions. One 
has a good deal of uprising air at all times. 4. Where is this belt? 5. What are 
its rain conditions? In another belt the air rises only at mountain slopes. 6. What 
sort of skies and what sort of lands should prevail at other points in this belt? 7. 
Which belt is it? Another has two different arrangements for causing the air to rise. 8. 
Which is this? Finally it is observed that two of these three belts occur necessarily in 
pairs. 9. Which ones? It is now possible to locate doldrum, trade -mountain and 
west-wind rainfall on the blank map. 

EXERCISE 20.— Our Irregular Rainfall 

91. Examine the table below of rainfall at Lansing, Michigan. 1. In what month 

is the rainfall greatest? 2. In what least? By what percent of the average monthly 
rainfall (2.77 inches) is it least? 4. In how many years does the table show that the 
wettest month had less than the average rainfall? 5. What percent of all the years is 
that? 6. Has summer or winter greater rainfall here? 7. Is that good or bad for 
our crops? Construct a diagram of four horizontal lines one above the other with their left 
ends in the same vertical line. The length of each line will represent the sum of the rain- 
fall of three consecutive months, one for the three of greatest and one for each other group 
of three months. Let one -half inch in the diagram represent one inch of rainfall. 



Yhar 


J.\N 


Fhb. 


M.^R. 


Apr. 


May 


Junk 


July 


Aug. 


Skpt. 


Oct 


Nov. 


Dhc. 


Ykar 


1880 


2 67 
2.27 
1.13 
0,98 
1.92 
1.59 
2 27 
3.36 
1,69 
1.67 
2.71 
1.07 
1.05 
1.84 
1.75 
2 66 
1 11 
3.62 
3.77 
2.05 
1.43 

i.e-? 

38 
1,54 
2.82 


1.85 

3 92 
2.59 

4 49 
3.24 

45 

1 64 

5 87 
1 74 
1.02 
1.85 
2,35 
1 64 
2.31 
1 67 
0.62 

1 08 
1,22 

2 16 
165 

2 84 
1 26 
0.56 

3 10 
1.53 


2.00 

2.14 
3 66 

34 
3,71 
6.40 
2.83 
1.30 
2.02 

1 14 
1.31 

2 48 
1.49 
3.78 
1.26 
1.14 
1.15 
3.20 

3 73 
,3.17 

2.20 
2,97 
4.12 
1.52 
3.87 


7,06 
1.65 
1.85 
1.89 
2,12 
2,38 
1.51 
0.98 
1.29 
1.70 
3 23 

2 45 
2.40 
530 

3 31 
1.12 
2 05 
2.43 
2.04 
1.93 
2 30 
2.29 
1.69 
4,40 
1 70 


6.81 
2,97 
4.33 
6.31 
4 34 
1 85 
3.00 
2.12 
3.65 
3.86 
6 22 
1 84 
6.'31 
4 08 
6.51 
2.05 
2.67 
3.44 
2,16 
3.28 
4.25 
2,67 
3,91 
2.07 
3 60 


6 96 
3 66 
5 51 
9.91 

3 09 
5,88 
2.14 
1.45 
2.07 
3.65 

4 03 
2.26 
4.81 
7.19 
1.81 
1 24 
3.39 
3 68 
4.55 
1.15 
2.19 
3.75 
7.07 
4.16 
2.79 


6.00 
1.63 
184 
10.12 
3.24 
2.04 
0.64 
1.68 
1 80 
2.67 
52 
2.91 
3,08 
0.98 
1.45 
1.72 
7.10 
7.36 
1.46 
2.62 
5.09 
6 33 
6.99 
4.79 
2.15 


6 02" 

2.05 

4.04 

0,21 

1.34 

6 75 

5.70 

0.93 

1,84 

0,18 

3.06 

5 27 

3.26 

73 

0.00 

5.38 

3 28 

2.0^ 

2.99 

33 

3 86 

3 24 

39 

5.68 

2.76 


4.13 
3 24 
1.07 
3.37 

2 71 

3 46 
6 05 
5.53 
2.06 
0.83 
2.39 
1.37 
2.80 
2.34 
2.76 
0.86 
6 27 
0.91 
2.53 
2.24 
1.27 
1 88 

■ 5 66 
3.92 
2.35 


2 84 
5 60 
3.10 

3 64 
6.13 

3 60 

1 15 

2 28 
3,03 
75 

4 96 

77 
1.00 
4.55 

1 98 

87 
0.87 
2.14 
3.66 
3.11 
3.51 
4.87 

1 65 
1.99 
2.20 


2.38 
4.39 
1.75 
4 08 
1.60 
3.05 
1.37 

2 06 

3 33 
2 59 

2 91 

4 39 
2.61 
2,46 
1.05 

3 91 

2 98 

3 39 

2 60 

1 86 

3 88 
1.32 

2 30 
1.45 
07 


66 

1 76 
1 30 
0.93 
2.77 
2.86 
1.22 
2.5^ 
1 25 
2,68 
1.35 
1 89 
1.61 
3 96 
1.14 
5.83 
0.72 
1.95 
1.27 
1.61 
0.47 
2.90 
2.32 
2.06 
1.27 


49 


1881 


35 


1882 


?2 


1883 


46 


1884 


36 


1885 


40 


1886 


29 Vi 


1887 


30 


1888 


26 


1889 


23 


1890 


34 J^ 
29 


1891 


1892 


32 


1893 


39 J4 


1894 


25 


1895 


27 


1896 


33 


1897 


35 


1898 


33 


1899 


25 


1900 


ii 


1901 


35 


1902 


37 


1903 


37 


1904 


27 






Average 


2,00 


2.11 


2.52 


2.44 


' 3.77 


3 93 


3.45 


2.84 


2.88 


2,73 


2.55 


193 


33 1 







At Boston the annual rainfall is 45.4 in. 
distributed as in the table. 

Fill out the Lansing columns. 









Boston 


Lansing 








Inches Per Ct 


Inches Per Ct 


Feb., 


Mar. 


Apr... 


.. 11 4 25 




May, 


June, 


July 


.. 10.5 23 




Aug. 


Sept. 


, Oct 


., 11.5 25 




Nov 


Dec 


Jan... 


.. 12.5 27 





45.9 



100 



59 

Maps 

92. The ball shape of the earth makes it impossible to draw maps correctly on any- 
thinj^ but a ball. Any map on flat paper is necessarily somewhat distorted. A familiar 
illustration is the cracking of a half orange peel that has been removed intact in its natural 
form, on pressing it down on the table. Another good one is had when you attempt to 
wrap a ball up in paper. Flat paper cannot be accommodated to it. Such surfaces — those 
to which a flat paper cannot be adjusted by mere rolling or wrapping, are known as 
warped. A trial, however, will quickly show that for a small part of the earth's surface, 
the disagreement between the ball surface and a plane is not very great. A circle of paper 
half an inch in diameter, placed upon a six-inch globe, comes near enough to re.sting upon 
the surface to make the part of the map traced through it fairly identical with that on the 
globe. Such a circle on that scale is 660 miles in diameter, about big enough to contain 
all the Great Lakes and the country about them; the whole of the British Islands, or any 
European country except Russia, Sweden or Norway. So there are many maps in which 
the distortion is of little account. Maps of whole continents, however, are necessarily 
somewhat distorted, and no map of the whole world, or even a hemisphere, can help mis- 
representing shapes and sizes. Different methods of map-drawing, or " projection," as it 
is called, are devised to render maps of large areas available for various purposes, one con- 
sidering the needs of the navigator, another that of persons wishing to compare areas, and 
others wishing a map that gives a comparative view of the whole world at once. The 
study of projection utilizes the highest skill of the mathematician. But simple construc- 
tions on the surfaces of cones and cylinders will give good results that a very moderate 
knowledge of geometry makes intelligible to any one. The device by which maps are 
drawn on the globe is the use of latitude and longitude, parallels and meridians. Some- 
thing of the sort is rendered necessary by the fact that a ball has neither a beginning nor 
an end. 

93. It is an error to teach a definition of these two coordinates and fail to use them. 
They should be used to find places before they are named at all, and the name only intro- 
duced when it becomes irksome and roundabout to get along without it. The first phrase 
should be that Cape Town, for instance, is 34° south of the equator, or perhaps even 
three and one -half latitude spaces, if that is the way your cheap globe is divided, not that 
the latitude of Cape Town is 34° south. That is, the word latitude is better introduced 
after the idea is familiar. In continent maps a network of parallels and meridians for 
every tenth degree will be found most convenient, and intermediate points are easiest 
found if even ten degree spaces are used; 10°, 20° and 30°; not 13°, 23° and 33°. The 
drawing of any map, in the first place, depends on finding the latitude and longitude of all 
the places. Usually a number of these are known, and others are guessed at. The lati- 
tudes and longitudes of the shores of the Great Lakes were very little known 50 years ago, 
as the following map of the region shows when put with a modern map (Fig. 36 from 
Bancroft's History of the United States, 1852.) At present we are almost equally ignorant 
of the interior of the State, but the Lake Survey has established the shore lines by accurate 
determination of latitudes and longitudes. 



60 




Fig. 36. The Great Lakes in Bancroft's History of the United States (ISS2) indicated by 

the heavy lines 

To Draw a Net for a Map of North America on the Scale of the Six inch Globe 
94. Materials: A well -sharpened pencil, a flexible rule divided to tenths of an inch 
and perforated with a small hole for the pencil point, at inches, and a needle. This rule 
is used to draw circles of any radius up to 12 inches, by thrusting the needle through at 
any division, and putting the pencil through the perforation. 

1. Take a sheet of good paper at least 5i inches each way. 

2. With a sharp lead pencil draw a faint line through the middle of the sheet, par- 
allel to its two short edges. 

3. Put two dots on this line four inches apart, the lower one ^/jo of an inch from the 
bottom of the sheet. Call this line the middle meridian, and keep the paper before you so 
that the line points from and towards you. 

4. Draw cross lines through the dots and bisected by them, each 4 inches long. 

5. Connect the ends of the cross lines, making a four-inch square, bisected by the 
middle meridian. 

6. Outside this square draw another whose sides are separated from its sides by a 
space two-tenths of an inch wide. This gives the four-inch square a double frame in 
which to number our net work. We may begin by numbering our middle meridian 100° 
at top and bottom. 



61 



7. On the 100th meridian, one-tenth of an inch above the upper line of the bottom 
frame, place a dot. 

8. Place another 5 inches higher on the same line extended. 

9. Draw an arc of circle as long as the paper will allow, and with 5-inch radius from 
this last point (8) as a center. The needle is pushed through the 5 -inch division on the 
rule just on a line with the inner ends of all Vio-inch divisions like the little perforation on 
the zero line. The point of the needle is now stuck into the dot (8), and the required arc 
drawn with a pencil point held in the perforation on the zero line. This arc, which is the 
parallel of 10° north latitude, may be numbered in the frames to right and left. It is 
drawn right across both frames intentionally. We need it so; but all other parallels and 
meridians will be drawn only from side to side of the inner square. 

10. To draw the other parallels use alw?ys the same point (8) as a center, and 
always insert the needle there, but the needle is to pass through the rule at points each 
time 0.52 of an inch nearer the perforation than for the next parallel below. Thus for 20° 
the radius will be 4.48 inches, and the interval is taken a little less than 4.5 inches. For 
30°, 3.96 is used, and so on. Draw the parallels up to 80° in this way, ending each at the 
inside line of the frame, and number at both ends. 

11. To draw the meridians lay off 
on the 10° parallel equal spaces of 0.56 
of an inch to right and left from the 100° 
meridian out to the edge of the paper. 
Take the needle from the rule, stick it 
in the center point (8), and placing the 
rule from this to the divisions, just made 
on the 10° parallel, one by one draw the 
meridians, or the parts of them that fall 
within the inner frame. Now number 
the meridians, and the net is ready for 
the map. As it very closely resembles 
the net on a six-inch globe in shape and 
size, the map drawn on it will resemble 
that drawn on the globe very closely. 
Fig. 37. Net for North America Fig. 37 shows the result. 

EXERCISE 21 

95. On a sheet of the perforated drawing paper from the back of the book, construct 
a net for North America, for a nine-inch globe. Ali^ measures should be half as 
LARGE AGAIN AS IN PARAGRAPH 94. Why? Draw the middle meridian the long way of 
the paper. Extend the 10th parallel as far right and left as possible and divide for meri- 
dians. To draw the meridians for the upper right and left corners of the map, repeat the 
subdivisions made by the meridians on the 60th parallel. 

96. Draw a net for Europe for a ten -inch globe. Elements for continent maps, scale 

of the six -inch globe: — 

Radius Parallel 10° Long. 10° Lat. Inner Frame 

5.0063 10° N. .5616 .5176 4 by 4 

3.3879 30° N. .4844 ,5221 3 by 3 

5.0063 10° N. .5616 .5176 5 by 5 

7.4328 10° S. .5276 .5226 3.5 by 3 

9.0733 10° N. .5675 .5159 3.5 by 4.5 

.,-,- --,— .4944 .5236 4.2 by 4.2 




North America. 

Europe 

Asia 

Australia 

South America . 
Africa , 



62 




EXERCISE 22.— To Make a Net for Australia on the Scale of the Six-inch Globe 

97. Elements: See § 96. Shortened direc- 
tions: 1. Paper from back of book. 2. Mid- 
meridian, long way of paper. 3. Two dots, ij 
inch from top of paper, and the other 3 inches 
from that. 4. Cross lines 3i inches long 
through these points. 5. Complete rectangle 
3x3^ inches. 6. Outer rectangle ?io inch away. 
7. Dot 2/io inch below lower line of upper 
frame. 8. Another 7.43 inches lower for center 
of parallels. 9. 10° parallel S. from this 
center, with radius 7.43 inches. 10. Other 
circles with radii successively 0.52 inch smaller. 
11. Meridians distant 0.53 inch on the parallel 

10° S, BEGINNING HALF A SPACE TO THE RIGHT 
AND LEFT OF MID - MERIDIAN LINE AS IN FiG. 38. 

In this southern hemisphere map net, of course the 
Fig. 38 shows the appearance of the net reduced in size. 

Map Scales 

98. On any map: 1. Note the number of degrees in a latitude space. 2. Turn 
that into miles by multiplying by 69. Why? 3. Measure a latitude space along a meri- 
dian to the nearest hundredth of an inch. 4. Divide the miles of (2) by the inches of 
(3) to get the miles to an inch. Carry your work to tenths to be sure of the unit. 5. 
To get the fraction of nature turn the miles of (4) into inches by multiplying by 5280 X 12 
=63360. 

Exercise 23 

99. Find the miles to an inch and the fraction of nature, of each of the following 
figures in this book: 1, 2, 36, and of the weather map on page (41) Do the work neatly 
with all sums and divisions worked out in full, showing clearly the results attained. This 
should be brought to class on loose sheets ready for " handing in." 

100. Meridians and parallels may also be drawn on a cone, and the size of the cone 
so selected that part of its surface shall come very near identity of shape with a moderately 
wide belt around the globe. The cone, of course, may be made by bending a properly cut 



Fig. 38. Net for Australia 
meridians converge downward. 




Fig. 39. Cone for North America intersecting sphere 



63 



sheet of flat paper (§ 102), so that the map drawn on it is available for book use when 
unrolled. The cone of paper may be set upon the ^lobe as a hat on one's head; in which 
case it touches the globe in a circle that may be called its circle of tangency and the cone a 
tangent cone, or it may be thought of as cutting through the globe in two circles of secancy 
and the cone a secant one. This is illustrated in Fig. 39 and allows a wider belt of cone 
and globe to approach coincidence. Fig. 39 shows the secant cone for a map net for North 
America, which may be said to extend from latitude 10° north to 70° north. It is seen 
that the middle belt of this latitude extent, 25° to 55°, lies on the globe with the surface of 
the cone close under it, and the two outer quarters of the latitude extent, 10° to 25° and 
55° to 70° lie on the globe close under the cone's surface. If the map be drawn on this 
cone it is very nearly identical with the same map on the globe. The exercises provide 
necessary practice in construction for any given scale on fiat paper, so as to give nets that 
when folded come into such positions as shown in this figure. 

101. The shape of the earth is assumed for the present purpose to be a perfect sphere, 
its diameter 7912 miles. As the polar diameter is 26 miles shorter than the equatorial, or 
2%9i2 of it =y304='<'%; on a globe 6 inches in diameter the polar dimension is only 2/100 of an 
inch shorter than the equatorial, not a perceptible quantity for ordinary purposes. An 
orange does not at all well illustrate the earth's shape, being excessively flattened. 
Polar flattening is not a thing to be taught to children, its appropriate place in the curricu- 
lum being part of the physics work in the High School. Degrees of latitude are therefore 
regarded as all equal. It will, of course, be remembered that degrees of longitude vary 
from nothing at the poles, to the full value at the equator, where they equal degrees of 
latitude. 

102. We examine these common kitchen funnels to find what angle their sides make 
with each other. What is it? Why that value, and why are they all alike? It will help 
to examine the cone made by rolling a small semi -circle of paper. We shall now find the 
cone for North America intelligible. 

On a sheet of Manilla paper 12 inches square, that 
will be supplied in class, draw a circle with a 5 -inch 
radius. Draw one radius as a dotted line, marking the 
end on the circumference 0. On our net for North 
America, 10° longitude on 10° north measured 0.56 
inch. I/Ct us find the whole circle. How many times 

distance from 

circle with the 
. It will appear, 

seems strange to 




'270 



Fig. 40. This circle cut along the 

solid radius and folded to overlap 

the sector marked, becomes a cone 

for a map of North America 



0.56 inch is that? Measure that 
around the circumference of your 
flexible rule and mark the end 360° 
perhaps, somewhat as in Fig. 40. It 
have 360° only a part of a circle. Draw a solid line 
radius from the center to 360°. Cut the paper from 
circumference to center along that line with shears. 
Bring the and 360 together by overlapping the rest of 
the circle. You have now the cone on which North America is supposed to be drawn, 
for it has a five -inch radius and 10° of longitude on the 10° parallel is equal to 0.56 inch. 
EXERCISE 24. — To Construct a Figure Showing the Elements of a Net for Europe 

103. Draw a circle of three inches radius. Measure after drawing to be sure it is 
exact. Draw two diameters at right angles. Consult the map of Europe, Fig. 2 

Fill in answers to the following questions. The letters in Fig. 41, will help the student 
to find what points are meant by the questions. Measurements cannot be taken from them, 
as the circle is not of 6-inch diameter, nor is the cone one for Europe. 



64 




Fig. 41. Section of cone intersecting sphere 
1. What is the northernmost latitude of Europe to the nearest degree? (H) 2. What 

is the southernmost latitude of Europe? (I,) 3. Over how many degrees of latitude 
does Europe extend? (H L) 4. What is the middle latitude? (K) 3. What two 
latitudes are intermediate between the middle and extreme latitudes? (B and C) Locate B 
and C on the arc with the thin paper quadrant. Draw the line through B and C, extended 
to cut the axis of the earth in A. D, the southernmost parallel used for Europe, we will 
call 30°. 6. Why is 30° a better value than 35° or 40°? 7. D is how many degrees 
distant from C? 8. C is how many degrees from B? 9. C is how many inches and 
hundredths from B in a straight line? 10. That makes one degree of latitude how long 
on the straight line AD? 11. How long, then, is the 10° latitude space on the map net 
for Europe? 12. How far in inches and hundredths is D from C along the line AD? 
(See 7). Locate D by measurement. Measure AD and you have the slant height of the 
cone to the southern parallel for Europe. This is also the radius with which we draw the 
circle on flat paper that may be folded into the 30° parallel. (See § 66). 13. Draw 

DM parallel to EE. It is the radius of the parallel of 30° on the cone. Measure it to 
the hundredth of an inch. Multiply it by 2- to get the circumference of the circle, and 
divide by 36 to get 10° on that circle (more simply since ^=0.1745) multiply DM by 



0.1745. 
sought. 



This gives us 10 longitude on 30 North. 11, 12 and 13 are the elements 



65 

EXERCISE 25.— Find Elements for Drawing the Map of Africa 

104. State the northernmost and southernmost latitude in Africa. As they are about 
equal, it appears that the points B and C will be equal distances north and south of the 
equator. When a line is drawn through them to represent a cone intersecting the sphere, 
it is found to be parallel to the axis. It does not cut the axis, therefore, and the map is to 
be drawn on a cylinder instead of a cone. If we call the two intersections of the cylinder 
and sphere in 17^° north and 17^° south, 10° latitude is determined as usual by measuring 
the space BC between them, and regarding it as representing 35° of latitude. In longitude, 
as all circles on the cylinder are equal, we find Vse of the circle through either B or C is the 
required 10°. Find the circumference by the radius let fall from B or C perpendicular to 
the axis. As a cylinder has an infinite slant height, the parallels are all straight lines, and 
the net has only two elements, 10° latitude and 10° longitude. It has rectangular meshes. 
Draw the net on the scale of the 9 -inch globe. 

Temperatures 

105. The usual data for temperatures are isothermal lines. They always represent 
temperatures reduced to sea level, though practically all geographies and physical geogra- 
phies fail to mention that fact. It is the best way to draw isothermal lines. All meteor- 
ologists know it and how to use such a map, but teachers and school children do not. 
If a teacher tries to learn from such a map the temperature on the summit of the Himalayas 
she finds it to be 50° or 60° in winter, and 80° or 90° in summer. Of course she knows 
there is ice and snow up there the year around and the map cannot be right. She does 
not know it has to be corrected for altitude before any of its indications become those of 
the actual surface, and finding it mentally indigestible she wisely lets it alone in all her 
work. Koppen's map on the contrary is for actual surface temperatures, and while it 
suffers certain defects inherent in all such maps, it does give a rough idea of the actual 
temperatures all over the surface of the earth and a fairly accurate one in those regions 
where men live. Note what our diagram indicates on the Himalayas. 

106. Temperatures. North America. Fig. 43 
1. What ocean shores are always cold? 2. What ocean has shores with hot 

summer and cold winter? .3. What parts of Mexico are always hot? Why? 4. What 
temperature has Mexico City? 5. What temperatures prevail in most of Canada? In 
most of the United States? In Mexico? 6. What sort of summers and winters has 
Florida? Maine? 7. What three types of temperature occur on the California coast? 
8. Name three large cities with hot summer and cold winter? 9. Name two with mild 
summer and cold winter? 10. Name one with hot summer and mild winter? 

107. Temperatures, Europe. Fig. 42. 
1. State England's summers and winters. 2. Name other countries of similar 
temperature. 3. State the temperature of Portugal. 4. Compare North Sea-Baltic 
countries with Mediterranean countries. 5. What different sorts of summers occur in 
Russia? Winters? 6. What temperature type is most widespread in Europe? 

7. Name three large cities with hot summers and mild winters. 8. What ones can you 
name with mild summer and cold winter? 

108. Temperatures. Asia. Fig. 42 
1. What parallel approximately bounds most of cold Asia. 2. Locate and bound 
other cold regions? 3. What parallel bounds hot Asia? Exceptions? 4. Where 
are the hot-and-cold regions? 5. Explain the interruptions. 6. Name three 

countries that have hot summers and cold winters. 7. Where is it mild the year 

around? 8. State the temperature of India, China and Japan. 



6g 



Temperature REciioiig 




Fig, 42 
LEGEND 



SHADE 



Black - 

Vertical lines 
Horizontal lines 
Slanting lines 
Blank - 



TEMPERATURE 
Always Mild 



DETAILS 
Hottest month averages under 68° 
coldest over 50° 
Always Cold ... Warmest month averages under 50° 
Always Hot - - - Coolest month averages over 68° 

Hot summer and Cold winter Averaging over 68° and under 50°* 
One season Mild the other Toward the Cold areas the Extreme 
Extreme season will be a Cold winter, toward 

the Hot areas a Hot summer. 

*For at least a month each 



67 



OF theI World 




Redrawn from Koppen as given by Ward in Bulletin Am. Geog. Soc. July, 1905, with slight altera- 
tions in United States. 

It will help the eye in reading these diagrams if the student will now shade the Cold areas a very 
pale blue with a colored pencil,* the Hot areas a pale red, and the Hot and Cold season regions with a 
red line on the first, fifth and ninth spaces between the slanting lines and so on with a blue one on the 
third, seventh and eleventh, thus making lines alternately red, white, blue, white and so on. 

In coloring the Cold areas do not overlook a small one between the thirtieth and fortieth parallels 
of north latitude. If the map were large enough to show them there would be other blue dots and lines 
on various other high mountain peaks and crests. 

*The six School Crayons In assorted coloi-s sold in a box for five cents by the American Lead Pencil Co., are 
excellent for tinting maps. 



109. Temperatures. Africa. Fig. 42. 
i. iyocate and bound and explain the mild areas. 2. lyOcate and bound the hot- 
and-cold regions. 3. Give the parallels approximately bounding the hot regions. 4. 
Where in Africa are the cold winters and mild summers? 5. Explain and tell whether 
people probably live there. 

110. Temperatures. South America. Fig.43. 

1. Locate and bound and explain the "always mild" regions. 2. Locate and 
bound the "always hot" regions. 3. Where, if the scale of the map were large enough 
to show it, might there be thin lines of dots of "always cold?" 4. What percentage 
of South America has hot -and -cold seasons? 5. Name a large city with hot summer 
and cold winter. 6. State the temperatures of Bogota, Lima, Rio Janeiro and Caracas. 

111. Temperatures. Australia. Figs. 42 and 43. 

1. Where are the hot regions? 2. What regions are always mild? Why? 3. 
What towns have hot summer and cold winter? 4 State the temperatures of New 
Zealand. 5. State the temperatures of Melbourne, Sydney and Wellington. 

112. Rainfall for June, July and August. North America. Fig. 45. 

1. Where are two areas of scant rain? 2. What percentage of Canada has light 
to heavy rain? 3. State the rainfall of the Pacific Coast in three items. 4. State it 
for the United States. 5. State it south of the 30th parallel 

113. Rainfall for December, January and February. North America. Fig 47. 

1. State it for the Pacific Coast. 2. State it for the region south of the 30th 
parallel. Include the islands. 3. Locate the heavy rainfall of the eastern United 
States. 4, Locate the scant rainfall of the continent. 5. What two areas of heavy 
rain seem to have moved in latitude from summer to winter. 

114. Rainfall of June, July and August. Europe. Fig. 44. 

1. Explain the heavy rain of Great Britain and Scandinavia. 2. By what mech- 

anism does Russia get its rain? §90 3. Compare the rain of the Baltic -North Sea coun- 
tries with that of the Mediterranean. 4. State the rain of Germany. 

115. Rainfall of December, January and February. Europe. Fig. 46. 

1. What general movement of the rains in latitude has occurred? 2. State the 
rainfall of Germany. 3. State the rainfall of the Mediterranean countries. 4. Com- 

pare east and west Europe. 

116. Rainfall of June, July and August Asia. Fig. 44. 

1. Where are the heavy rains? 2. Where are the light rains? 3. ■ Where are 
the doldrum, trade -mountain and westerly rains? 4. Compare with Europe in (l) and 
(2). 5. Where are the two dry regions? 6. Is this more like Europe or North 
America? Why? 

117. Rainfall of December, January and February, Asia. Fig. 46. 

I. What part of the continent is occupied by areas of heavy rain? 2. Compare 

with North America and Europe. 3. Why should this be so? See text § 75, and 

compare facts for June, July and August. 4. What-populous countries have rain at all 

seasons. 

118. Rainfall of June, July and August. Africa. Fig. 44. 

1. Locate and explain the northernmost patch of heavy rain. 2. Locate and 
explain the southernmost patch of heavy rain. 3. Locate and explain the middle belt 
of heavy rain. 4. Locate and explain two dry regions. 



6$ 

119. Rainfall of December, January and February. Africa. Fig. 46. 

1. Locate and explain the northern belt of heavy rain. 2. Locate and explain 
the southern belt of heavy rain. 3. Locate and explain two dry areas. 4. Where 
is there heavy rain in both seasons? 5. Lake Chad is in 13° north latitude, 13° east 
longitude. What difference might be observed in it from July to January? 6. In what 
month should the Nile be in flood? Allow a month or two for the rains to drain from 
equatorial swamps into the Nile valley. 7. State three African illustrations of seasonal 

migrations of rain. 

120. Rainfall of June, July and August. South America. Fig. 45. 

1. Are these summer rains? (Have you tinted as suggested under the legend?) 

2. State the position of the doldrum rains. 3. Are there any trade wind rains? 4. 
Which are clearly west wind rains? 5. Describe the rainfall of the Pacific Coast. 
6. Tell the shape, size and position of the dry area. 7. Describe the rainfall along 
the Andes. 

121. Rainfall for December, January and February. South America. Fig. 47. 
1. Is this winter rain? 2. Where are there trade wind rains? 3. Explain the 
dry area in 10° south latitude. 4. Was there any seasonal migration of rain? 5. 
Describe the dry areas. 6. What regions have rain in both seasons? 7. Describe 
the rainfall of the Argentine Republic. 

122. Rainfall of June, July and August. Australia. Figs. 44 and 45. 
1. What season's rain is this? 2. What two wind belts yield it? 3. What 
parts of Australia are dry? 4. State the rainfall of New Zealand. 
123. Rainfall of December, January and February. Australia. Figs. 46 and 47. 
1. What rains are those of the north? 2. State the rain of southern Australia. 

3. What parts of Australia and New Zealand have rain in both seasons? 4. What 
rain belts have now moved south? 

124. Plant Regions. North America. Fig. 49. 

1. What percent of Canada is summer forest? Of the United States? 2. What 

three other types of vegetation occur in the United States in order of area occupied? 
3. Where shall a New York man go to get quickest to a wet tropic forest? 4. How 
much desert and grass land has the United States?* 5. What do we call the grasslands 
of North America? 6. Why are they not as populous as the summer forests? 7. 
Explain the forest of south eastern United States. 

125. Plant Regions. Europe. Fig. 48. 

1. What two types of forest occur in Europe? Where? 2. What percentage of 
Europe is in summer woods? 3. Distinguish steppes from grass lands in Hungary and 
Russia. 4. Give reasons. 5. What North American types of forest are wanting? 

* It has long been a vexed question as to the absence of trees In a soU which seems to be most suitable for their 
development. Probably the most ancient explanation was the occurrence of prairie fires, but it seems evident 
that some general natural condition rather than an artificial one is responsible for such an extensive area. A 
possible explanation is as follows: The extensive plains of the West develop the strong and dry winds which 
prevail over the prairie region, and this brings about extremes of heat and drouth, in spite of the character of the 
soil. In such conditions a tree in a germinating condition could not establish itself. The prairies, therefore, 
represent a sort of broad beach between the Western plains and the Eastern forests. The eastward limit of the 
prairie has probably depended upon the limit of the dry winds, which are gradually modified as they move east- 
ward, until they cease to be unfavorable to forest growth. The forest does not begin abruptly upon the eastern 
limit of the prairie, but appears first a clump of trees, with interspersed meadows, and finally as a dense forest 
mass. Of course, the forest display of the eastern border of the prairie has been immensely interfered with by 
man. — Ooulter, Plant Relations, page 236-8. 



70 



Rainfall of the World in June, July 




SHADE 

Ruled lines - 

Dots - 
Blank - 



Fig. 44 

LEGEND 

RAINFALL DETAILS 

Heavy - - More than ten inches of rain and melted snow in the three 

months. 
Light - - From six to ten inches in the three months. 
Scant - - I,ess than six inches in the three months. 



71 



And August (includes melted snow) 




Fig. 45 

After Supan. 

It will add much significance to the diagrams if the student will now tint with pale red the shaded 
and dotted areas north of the tropic of Cancer, 23i° north, as symbolic of summer or warm season rains, 
and with pale blue the shaded and dotted areas south of the tropic of Capricorn, symbolizing cold season 
or winter rains. That the zone within the tropics remains uncolored means that it does not have true 
summer and winter. 



ni 



Rainfall of the World in December, January 




SHADE 


RAINFALL 


Ruled lines - 


Heavy 


Dots - 


- Light 


Blank - 


- Scant 



Fig. 46 
LEGEND 

DETAILS 

- More than ten inches of rain and melted snow fall in 

the three months. 

- From six to ten inches in the three months. 

- Less than six inches in the three months. 



73 



AND February (including melted snow) 




Fig. 47 

After Supan. 

It will add much significance to the diagram if the student will now tint with a pale shade of blue 
the ruled and dotted areas north of the tropic of Cancer, 23i° north latitude, as symbolic of winter or 
cold season rain, and the similar areas south of the tropic of Capricorn with pale red, symbolizing 
summer or warm season rains. The Intertropical region remains uncolored, as being without true 
winters and summers. 



74 



PivANT Regions 






Fig. 


48 




LEGEND 




SHADE 


VEGETATION 


1. 


Black 


Wet Tropic Forests 


2. 


Black Spots 


Wet -season Tropic Forests 


3. 


Dots ---... 


Tropic Open Woods 


4. 


Black Bars - . . . . 


Sub -Tropic Wet Forests 


5. 


Black Triangles - . . . 


Leathery Leaf Thickets 


6. 


Circles --..-_ 


Summer Forests 


7. 


Stars of sixty degrees like a snow-flake 


Alpine Plants 


8. 


Broken lines - - - . . 


Grass Land or Steppes 


9. 


Small Dots - - - . . 


Tunrda 



75 



OF THE WORtD 




Fig. 49. 

After Schimper dictaii<S 

1. Warmth and rains at all seasons. Air plants abound. Forests are quite impassible. 

2. Less dense. A season of drouth compels trees to drop their leaves and rest. Along the streams this 

does not happen. Temperature still high. Air plants less numerous. 

3. Warm but severe season of drouth allows only isolated trees in broad expanses of bush or grass. 

Continuous forest along streams only. 

4. Less luxuriant than near the equator. Evergreen; but interspersed are trees that drop their leaves, 

not in dry, but in a cold season — winter. 
5 Always in regions of winter rain, 30° or 40° from the equator. The leaves are tough enough to 
withstand considerable summer drought. Oleanders are typical. Trees moderate sized, gnarled 
and less abundant than shrubs. Trees stunted by getting water enough for growth in the cold 
season only. 

6. Moderate rain and winter cold severe enough to arrest growth or cause leaves to fall. These forests 

may usually be traversed without hewing a path, but have fine trees which get their growth in a 
moist summer. 

7. Stunted plants that live on cold, windy mountain summits. 

8. With forests along the streams. Increasing drought changes grass land to steppe, the steppe to desert. 

9. Low shrubs and herbs that imperfectly cover the ground which is frozen ten months in the year. 



76 

126. Plant Regions. Asia. Fig. 48. 
1. To what rainfall does the wet tropic forest correspond? 2. What Asiatic 
countries have deserts? 3. State the plant regions of China and India. 4. State 
the plant regions of Japan and Dutch East Indies. 5. What percentage of Asia has 
summer forests? What countries? 6. Where are the leathery leaf thickets? 

127. Plant Regions. Africa. Fig. 48. 
1. What types of forest are lacking? Why? 2. Equatorial Africa has many 
rivers. What report might a traveler along them make of the plant type there? 3. What 
is the real type? Why? See Fig. 31. 4. In what other parts of the world have we 
found the Cape Town vegetation? 

128. Plant Regions. South America. Fig. 49. 

1. What is the only plant type missing? Why? 2. What are the plant regions 
of Chile? 3. What those of the Argentine Republic? 4. In what wind belts are 
the wet tropic forests? 5. What large country has most of the tropic forests? 6. 
Why are alpine plants so much more abundant than in North America? 

129. Plant Regions. Australia. Figs. 48 and 49. 

1. What sort of forests prevail in the thickly settled parts of Australia? 2. Where 
are the leathery leaf thickets found? 3. Explain the forests of the north. 4. Why 
should New South Wales and the southern island Of New Zealand have plant regions so 
contrasted in position? 

SCALE OF TENTHS 

130. A little above the middle of one of the pages of quadrille paper darken one of the 
horizontal lines for a length of twenty squares. Eetter the left end O and the right A. 
On the vertical line passing through A^place ten dots, one on every second line from A up> 
Connect each of these ten dots with O by a fine pencil line. These oblique lines divide 
each vertical blue line that they cut into ten equal parts. It is plain that any line not over 
twenty squares long may be divided into tenths by standing it on the horizontal line and 

. shifting it sideways until its top cuts the upper line. It will then be divided as required. 

To Draw South America Freehand 

131. Lay the edge of a small square of paper along the sixtieth meridian on the map 
of South America, at page 77, and mark off one latitude unit — here ten degrees — from 
the lower right hand corner of the square. This is our unit length. From the same 
corner and along the same edge mark off two other lengths. These are the longitude 
spaces on the northern and southern parallels respectively, ten degrees north and fifty 
degrees south. With the scale of tenths determine the values of the two longitude spaces 
as percentages of the latitude space. This is done by standing the marked edge of the 
square upright on the base line of the triangle and moving it right or left until the mark for 
the latitude space comes against the topmost line when the lesser, southern, longitude space 
will be seen, by counting tenths and estimating hundredths, to be 71 hundredths of the 
latitude space. The longer space, however, is greater than the latitude space. 
This latter should be marked off on it and the value of the excess determined on the scale 
by letting the marked edge of the square slip down until the top of the space to be measured 
comes to the upper sloping line, when the estimate of the length of the fractional part is 
seen to be nine hundredths. The whole line is, therefore, 1.09 in terms of the latitude 
space. With any unit for the latitude space, therefore, we have to take 71 and 109 percent 
of this unit for the longitude values. 



77 



SOUTH AMERICA IN PROVINCES 




78 

132. Let us now draw a map with seven-tenths of an inch for our latitude unit: 

1. On the edge of a bit of paper lay off seven-tenths, five-tenths (or 71 percent of 
seven-tenths) and seventy-six hundredths of an inch (=1.09X0.7). 

2. Draw a straight line up and down the center of a sheet of paper about four and a 
half inches long, and beginning four -tenths of an inch down from the top, put a dot every 
seven -tenths of an inch for the parallels, which should be numbered ten north, zero and 
ten to fifty south. 

3. Place three dots to the right and two to the left of the middle line about on a 
level with the tenth parallel north, and curved about as that parallel curves in the map to 
be copied. They are to be seventy -six hundredths of an inch apart. 

4. Place similar dots on the fiftieth parallel south, but these are half an inch apart. 

5. For the meridians draw straight lines between the corresponding dots on the upper 
and lower curves. 

6. Draw the parallels freehand through the dots on the middle meridian. If pains 
are taken to see that they cross each meridian at right angles their curvature will take care 
of itself. 

7. The map is now drawn on its net in the usual way. 

133. With practice this procedure is simple and should allow the preparation of the 
map of almost any single country in four or five minutes. If coast lines are complex, a 
small mesh must be used, z. e. one of fewer degrees. Thus the main sinuosities of the 
Japanese coast may be drawn on a net of two degree mesh, like Fig. 52. A very great 
gain in time is made by using a mesh twice as large, as Fig. 53, and generalizing the out- 
lines. Such a map is still accurate in size and relation of parts, as one island to another 
and all to the mainland. If the time of making is shortened enough to make possible for a 
teacher blackboard illustrations that could not otherwise be presented to the class, the loss 
of minor items of coastline is quite insignificant beside the gain. The common habit of 
"wiggling" coast lines cannot be enough criticised. Between points that can be placed 
with accuracy the lines should be smooth. It will be noticed that in drawing the Japanese 
Empire the coast of Asia has been included. This should always be done, for the nearness 
of that coast is an important item of Japanese geography. So France and England are 
each drawn with the inclusion of the near part of the other's coast. Good maps of Europe 
always include Asia Minor and North Africa, and with each American state must be 
included at least parts of neighbor states. 



79 




Fig. 51 



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PLAN OF LESSONS 







Class Work 


Home Work 


1. 


(1-7) Distribution of People. 


(1-7) 


2. 


(1-7) 


" " 


(7-15) 


3. 


(7-15) 


( ( 11 


(16) 


4. 


(16) People in North America. 


(17) 


5. 


(17) People in Europe. 


(18-19) 


6. 


(18, 19) 


People in Asia and Africa 


(20, 21) 


7. 


(20, 21) 


South America and Australia 


(22, 23 and 24) 


8. 


(22-24) 


Rainfall 


(25-27) 


9. 


(25-27) 


Rainfall. 


(28-33) 


10. 


(28-33) 


Temperature, Ex. 1. 


(Ex. 1, 34-36) 


11. 


(34-37) 


Temperatures, Askabad Curves 


(Ex. 2, 38-40) 


12. 


(38-40) 


Insolation and Radiation 


(Ex. 3, 41-42) 


13. 


(41-42) 


Air and Ocean Temperature. 




14. 


Test. 




(Ex. 4, Ex. 5, 43, 44) 


15. 


(43, 44) 


Cuzco curves and clouds. 


(Ex. 6, 45-47) 


16. 


(45-47) 


Annual Temperatures. 


(Ex. 7, 50, 51; 


17. 


(50-52) 


Expansion Temperatures 


(52-56) 


18. 


(52-56) 


Expansion Temperatures. 


(Ex. 9, 57, 58) 


19. 


(57, 59) 


Isotherms. 


fEx. 10, 59) 


20. 


(59-60) 


Isotherms 


(Ex. 11, 61-63) 


21. 


(61-65) 


Balancing columns 


(65-67) 


22. 


f66-68) 


Barometers, Isobars. 


(Ex. 12, 68) 


23. 


(68-69) 


Relation of Pressure and Temperature. 


(70-72. Ex. 13) 


24. 


(70-73) 


Isotherms and Isobars. 


(Ex. 14, 74) 


25. 


(74-76) 


Cyclonic winds and monsoons. 


(Ex. 15, 76, 77) 


26. 


(77-79) 


Winds. 


(Ex. 16, 79, 80) 


27. 


(80) Wind Effects. 


(Ex. 17, 81, 82} 


28. 


(82) Foucault's Pendulum 


(Ex. 18, 82, 83) 


29. 


(83, 84) 


Winds, Water Vapor 


(84-86) 


30. 


(84-88) 


Water Vapor. 


(Ex. 19, 89) 


31. 


(89, 90) 


Rain Distribution 


(Ex. 20, 91-93) 


32 


(94) Draw net for North America 


(Ex. 21, 95) 


33. 


(95, 96) 


Net for Europe 10" 


("Ex. 22, 97) 


34 


(97, 98) 


Map Scales. 


(Ex. 23, 99) 


35. 


(99-102) 


Cones. 


(Ex. 24, 103) 


36. 


(103) Elements of Cones. 


(Ex. 25, 104) 


37. 


(104, 105) Elements Africa, Temperature. 


(106, 109) 


38. 


(106-109) Temp. N. Am., Eur., Asia, Africa 


(110-113) 


39. 


(110-113) Temp. S. Am., Australia, rains N.Am. 


(114-117) 


40. 


(114-117) Rains Europe and Asia 


(118-121) 


41. 


Test. 






42. 


(118-121) Rains Africa and South America 


(122-125) 


43. 


(122-125) Rains Australia Plants Europe and Asia 


(126-129) 


44. 


(126-129) Plants Asia, Africa, S. Am., and Australia 


(130-132) 


45. 


(130-132) Freehand South America. 


fl33) 


46. 


(.133) Maps Japan 






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